Author Archives: T.C. Kelly

About T.C. Kelly

Prior to his retirement, T.C. Kelly handled litigation and appeals in state and federal courts across the Midwest. He focused his practice on criminal defense, personal injury, and employment law. He now writes about legal issues for a variety of publications.

Seal of State of Florida and Gavel

Court Protects Right of Professors to Testify as Expert Witnesses

Expert witnesses can be drawn from all walks of life. Expertise does not always derive from a formal education. Mechanics and roofers, for example, often serve as expert witnesses based on their work experience.

Many witnesses nevertheless qualify as experts because of their academic training. College professors who perform relevant research are a logical choice when lawyers begin to search for an expert whose specialized academic background enables them to give expert testimony.

In November 2021, ExpertPages called attention to an attempt by the University of Florida to block three political science professors from giving expert testimony in a voting rights lawsuit. The dispute implicated the academic freedom of the University’s professors, as well as their First Amendment right to express opinions without interference by a government entity.

Silencing Experts

The Florida legislature, apparently unhappy that professors who act as expert witnesses call attention to troublesome legislation, enacted a law that prohibits a professor from engaging in “outside activities” that create a “conflict of interest.” A conflict can arise when a professor spends so much time on outside activities that the professor’s ability to perform job duties is impaired. More insidiously, the legislation states that a conflict arises when a professor’s outside activity “affects, or appears to affect, their professional judgement or obligations to the University.” 

The University adopted conflict policies to implement that directive. The policies require professors to report outside activities, paid or unpaid, to the University. They must also receive the University’s permission to act as an expert witness. The University thus made itself the judge of whether expert testimony might create the appearance of interfering with the professor’s obligations to the University.

Despite a long history of approving requests to testify as experts, the University denied the political science professors’ requests to testify as voting rights experts. According to the University, the testimony would create a conflict with the executive branch of state government, which in turn would create a conflict for the University.

The professors sued the University of Florida after the University rejected their requests to act as expert witnesses. Their testimony would advance the claim that Florida’s new voting law will suppress minority group voting by making it more difficult for people with limited incomes to vote. The professors have studied voting procedures and the ways in which those procedures affect voter turnout and the ability to cast ballots. 

The University’s Position

The University contended that the professors would be acting against the interests of the University by testifying. The University’s administration equated the University’s interests with those of the state’s executive branch. The dean of the University’s college of arts and sciences wrote: “Outside activities that may pose a conflict of interest to the executive branch of the State of Florida create a conflict for the University of Florida.” 

Governor Ron DeSantis is in charge of Florida’s executive branch. DeSantis is a strong supporter of the state’s new voting legislation. The position taken by the University would prevent any expert from offering any opinion that a sitting governor disfavors. The University thus ties approval of requests to give expert testimony on the content of the testimony.

At the same time, the University was instructing its employees not to make any statements to the media that were critical of DeSantis. University officials apparently feared that the governor would retaliate, and that the University’s funding would be jeopardized, if a University employee opposed any political position that DeSantis advocated.

The University’s assistant vice president for conflicts of interest took the analysis a step further. He contended that any testimony in a lawsuit against the state is adverse to the University because the University is a creature of state law. That position would make it impossible for any professor to testify in any lawsuit against the state, including lawsuits that have nothing to do with the University.

The professors argued that University employees routinely testify as private citizens and that their testimony does not speak for the University. After the professors sued the University for violating their right to free speech, the University decided to allow the professors to testify on their own time and without using University resources. The University declined to change its policy, however, retaining the freedom to decide on a case-by-case basis whether professors will be allowed to give testimony that University officials disfavor.

Court Decision Favors Expert Witnesses

A professor of pediatrics and two law professors joined the lawsuit, alleging that the University’s policies had also stifled their ability to testify as expert witnesses. The pediatrician was denied permission to testify about the efficacy of requiring children to wear masks during a pandemic. The law professors were denied permission to draft an amicus brief opposing the state government’s attempt to restrict the voting rights of felons who had finished their sentences.

All six professors asked the court to issue an injunction that would prohibit the University from interfering with a professor’s First Amendment right to express opinions in litigation. A federal district judge in the Northern District of Florida entered a temporary injunction that granted the requested relief.

The University apparently hoped that giving the professors permission to testify would cause the lawsuit to be dismissed as moot. Since the University changed its decision about the plaintiffs’ requests but did not change its policy, its mootness argument failed.

In a stirring decision that begins by comparing the University of Florida’s actions to the recent suppression of academic freedom in Hong Kong, the court discussed the relationship between the funding that the University of Florida needs to maintain or elevate its status as a top public university and the political goals of state government. The court concluded that the University’s desire to maximize funding by minimizing its employees’ private criticism of public policy is inconsistent with the First Amendment.

The court rejected the University’s argument that its employees forfeit their First Amendment rights by accepting state employment. There is a difference between speech as an employee and speech as a private citizen. Professors give expert testimony as private citizens. The court recognized that professors “have a First Amendment right to testify about topics related to their expertise in litigation against the State of Florida, and just because such testimony relates to their expertise—which is itself related to their work as public university professors—does not mean that it falls outside the First Amendment’s reach.”

The court was amazed that University officials “denigrated their own professors as being no better than two-faced mercenaries when they seek to testify as experts in their field in cases challenging Florida law.” Professors are not required to support or remain silent about arguably unconstitutional actions taken by state lawmakers simply because the professors are employed by the state.

The University’s conflict policy articulated no clear standard to guide the University’s decision to approve or disapprove a professor’s request to testify as an expert. The court concluded that the University’s attempt to give itself “unbridled discretion” to censor the testimony of professors who testify as experts is unconstitutional. The University’s “policy allows it to silence speech before it happens” and is thus a forbidden prior restraint of protected speech.

The University’s interest in protecting its funding from the wrath of petulant government officials does not outweigh the professors’ interest in free speech. The University’s attempt to protect itself was based on speculation about how the executive branch or legislature might react to disfavored testimony. Yet “the legal issues presented in the litigation did not directly implicate or involve [the University] in any meaningful way.” No actual conflict of interest existed. In fact, the University admitted the absence of an actual conflict after it was overwhelmed by bad press about its attempt to censor professors who testify as expert witnesses.

Litigation Outcome

The court granted a preliminary injunction that prohibits enforcement of the policy until the court rules on the lawsuit, either in summary judgment or after a trial. The handwriting is nevertheless on the wall. Keen observers understand that the judge “left scant doubt that his opinion of the school’s conduct was unlikely to change.”

Ironically, the University wants to maximize its funding to continue its quest to be ranked as one of the nation’s top public universities. Yet stifling the ability of professors to act as expert witnesses might drive faculty away from the University of Florida and toward educational institutions that respect academic freedom. The court’s rejection of the University’s censorship might actually help the University attract and retain faculty members who would otherwise be unwilling to work for an employer that does not respect their constitutional rights.

The judge’s decision is a victory for free speech and for the ability of public university professors to testify as expert witnesses in litigation against state governments. While the decision governs only the testimony of the plaintiffs and has no precedential value, other judges are likely to adopt its forceful reasoning if other public institutions attempt to infringe on the right of professors to express private opinions as expert witnesses.

Laptop with headset

Experts Help Justice Department Make Cases Against Capitol Rioters

The Capitol riot investigation has benefitted from people who recognized neighbors, co-workers, and relatives in videos that were posted to social media accounts. Many individuals who stormed the Capitol were either proud of their actions or thought their friends would be entertained by their antics. As they added evidence of their crimes to social media accounts, acquaintances who were shocked by the January 6, 2021 riot brought that evidence to the attention of law enforcement.

Within weeks, rioters who had treated their actions as a lark were scrambling to remove their posts from social media accounts. To conceal evidence of their presence inside the Capitol, individuals closed social media accounts, deleted pictures and videos from their phones, and even smashed their phones to hinder recovery of deleted files. Law enforcement has turned to amateur and professional experts to make cases against hundreds of participants in the Capitol breach.

Open Source Experts

Fortunately for law enforcement, journalists and other concerned Americans recognized the risk that evidence would be scrubbed from social media. Beginning on January 6, they began a collective effort to search Facebook, Instagram, and other social media sites and to archive the livestreams, pictures, videos, and narratives that they found. Open source experts used “automated social media scraping programs” to find incriminating evidence and created shared spreadsheets to catalog and archive their discoveries.

One individual used “open source machine learning and facial recognition software” to capture “every face from the 827 videos that were posted to Parler from inside and outside the Capitol building on January 6.” All of those faces were posted to a website. While some of the individuals who were outside the Capitol might not have trespassed, the site made it possible for individuals who recognized faces to contact law enforcement officers who could investigate further.

The evidence archive has been beneficial to law enforcement, but it has also promoted a broader search for the truth. False claims by politicians and cable media outlets that the riot was caused by antifa or left-wing agitators failed to gain traction, in part because archived video evidence failed to support those claims.

Facial Recognition Experts

Law enforcement officers were able to supplement the open-source archive with pictures and videos taken by security cameras within and surrounding the Capitol. With help from a variety of sources, law enforcement has been able to identify hundreds of individuals whose faces appear in pictures and videos.

While many individuals who breached the Capitol were identified by people who knew them, law enforcement officers turned to facial recognition experts to identify others. In some cases, experts received tips that identified people who were suspected of entering the Capitol, then used technology to find those individuals in videos of the riot.

In other cases, experts began with a picture of a rioter and compared the picture to databases that include photos from multiple sources, including mug shots, driver’s license photos, dating apps, and selfies found on social media. For example, experts using facial recognition technology were able to identify Stephen Chase Randolph, who was seen on video “assaulting multiple US Capitol Police officers.”

Cellphone Tracking Experts

Cellphone tracking experts gathered the “phone numbers of congressional members and staffers, responding law enforcement officers and agents, Secret Service protectees, responding medical personnel, and other authorized governmental employees” who were inside the Capitol during the riot. Cellphone tracking experts then used technology to identify cellphones that were present in the Capitol during the riot. 

The cellphone data came from GPS locations transmitted by the phones, as well as information about nearby Wi-Fi access points and Bluetooth beacons. By subtracting phones belonging to persons whose presence was authorized, authorities were able to identify phones that may have belonged to trespassers and rioters. That evidence contributed to the arrest of Jeremy Daniel Groseclose after experts concluded that a phone associated with Groseclose was probably inside the Capitol during the riot.

Expert Witnesses

None of the Capitol riot cases have gone to trial, in part because video evidence, selfies, and incriminating social media posts have provided compelling evidence of guilt in most cases. If cases do go to trial, expert witnesses are likely to pay a vital role.

While selfies have generally created clear images, it is not always easy to pick out faces from videos of the rioting crowd. Digital enhancement experts will likely testify about techniques they used to stabilize moving images, remove blurs, and increase the clarity of images. Combined with cellphone and facial recognition experts, the Department of Justice hope to present convincing expert evidence to prove the guilt of Capitol rioters. 

How Far Can Lawyers Push to Discover Evidence of Expert Witness Bias?

The potential bias of an expert witness is not usually a ground for excluding expert testimony. Bias goes to credibility and credibility is for the jury, not the trial judge, to determine. Before an expert can be excluded for bias, the bias must generally be so obvious that a judge can say as a matter of law that the witness is an unreliable source of information.

On the other hand, the bias of a witness is always a relevant issue in a trial. Lawyers generally rely on cross-examination as a tool to expose bias. However, the maxim that lawyers should not ask a question unless they know the answer should motivate lawyers to discover evidence of bias before the expert witness takes the stand.

Financial Bias

Unless an expert witness has a personal relationship with a party or a political axe to grind, an expert’s financial incentive to give favorable testimony is usually the strongest evidence of potential bias. The extent to which claims of financial bias are likely to sway a jury depends on the facts of the case.

Juries understand that expert witnesses are paid for their time. Everyone understands that being paid to testify creates a risk that the expert will slant testimony to favor the party paying the expert’s fee. That risk is captured in the German proverb, “Whose bread I eat, his song I sing.”

When each side calls a retained expert, however, the risk that experts will be viewed as hired guns tends to offset. One study suggests that the “hired gun” perception is strongest when an expert testifies frequently and earns substantial compensation from giving expert testimony.  The study also concludes that juries are most likely to view an expert as biased when they don’t understand the expert’s testimony. 

Lawyers can minimize the “hired gun effect” by assuring that the expert’s testimony is easy for the jury to comprehend. When juries think that an expert is making sense, they are less likely to dismiss expert testimony as the product of bias.

Discovery of Financial Bias

The Federal Rules of Civil Procedure require retained experts to disclose the amount of compensation they are being paid for their services “in the case.” A closer question is the extent to which a party can discover compensation paid to an expert, either by the same or a different party, in other cases.

Courts often draw a distinction between discovery of a party’s financial relationship with an expert and an expert’s income from broader employment as an expert witness. The issue has frequently arisen in cases involving independent medical examinations (IMEs) performed by doctors who are hired repeatedly by insurance companies. A jury might view a doctor’s substantial income from repeated testimony for the same insurance company as evidence that the doctor can be counted on to favor that insurance company. Allowing broad discovery of an expert’s income, however, arguably has a chilling effect on the willingness of professionals to act as experts.

Courts have attempted to balance an expert’s right to financial privacy against a party’s right to discover evidence of bias. An Arizona court, for example, concluded that it was inappropriate to use a subpoena duces tecum to obtain financial records before taking the deposition of a medical expert who performed an IME for an insurance company. The court viewed the “exhaustive” request for production of financial records, including tax returns, as unduly burdensome, at least as an “opening salvo” in discovery. The court concluded that the plaintiff’s lawyers should first pursue less intrusive avenues of discovery that might produce bias-related evidence.

A leading decision in Florida followed a similar analysis. The appellate court allowed a defense physician to be questioned about compensation paid for testimony in the plaintiff’s case. The court decided that a lawyer may also ask a defense expert who performs IMEs about the percentage of his or her income that was earned from testifying as an expert and the percentage earned from treating patients. Lawyers in Florida can ask for an approximation of the time the expert spends working as an expert witness, but cannot ask how much income the expert earns, either from all sources or from work as an expert witness. Another Florida decision gave lawyers greater latitude to inquire about historical income earned from the party in a case, as opposed to income earned from all work as an expert witness.

When courts limit discovery to relatively vague information offered during depositions (such as the percentage of time the witness devotes to work as an expert), whether the witness answers those questions truthfully can be difficult to determine in the absence of financial document discovery. The Arizona court offered a partial remedy to that problem by suggesting that financial document discovery might be appropriate when an expert is evasive, uncooperative, or untruthful. How parties can determine that answers are untruthful in the absence of financial document discovery is unclear.

Other courts take a more liberal approach to discovery. The Pennsylvania Supreme Court permitted interrogatories seeking discovery of all expert income earned each year during the past three years. A Kentucky court held that doctors who testify for insurance companies can be asked about the total amount of income they earn from performing IMEs. A Tennessee court agreed with courts “that have allowed expert witnesses to be questioned about the amount of income they earn from their forensic activities.” That court upheld a judge’s order for discovery of financial documents that would be filed under seal with the trial court to permit the judge to determine whether a recalcitrant doctor’s deposition testimony about his income was truthful.

Discovering financial information that might suggest the bias of a testifying expert is easier in some states than in others. Lawyers need to have a firm grasp of relevant court decisions in the jurisdiction that hears the case before they make a plan to uncover evidence of an expert’s potential financial bias.

Using Expert Witnesses in Arbitration Proceedings

Arbitration clauses are common in commercial contracts. Some employment agreements and user agreements (the online contracts that consumers never read before clicking “I agree”) also contain arbitration clauses. 

Arbitration has been promoted as a cost-effective alternative to courtroom litigation. That may or may not be true. The filing fee to start an arbitration can be considerably larger than the fee for filing a lawsuit. Arbitrators charge a daily fee; judges are paid by the public. Court reporters charge the same fee for depositions, whether the discovery is conducted in a civil action or an arbitration.

On the other hand, the motions that extend civil litigation are usually curtailed in arbitration. Cases generally proceed more quickly in arbitration, resulting in lower attorneys’ fees for clients who pay lawyers by the hour.

Expert Witness Disclosure and Discovery in Arbitration Proceedings

Plaintiffs frequently ask an expert witness to evaluate a case before they decide whether the case is worth pursuing. For example, when a consumer purchases a product from an online vendor that injures the consumer, a lawyer might want an engineer to examine and test the product to decide whether the product’s design made it unreasonably dangerous. A lawyer may rely on that opinion when they lawyer decides to bring a product liability case.

In federal court, a consulting expert’s opinion is not usually discoverable. If the lawyer wants the expert to testify in court, however, the lawyer must disclose the expert and the expert must prepare a report that complies with federal rules. Communication between the expert and a lawyer might be shielded from discovery, but — as is true of the rule shielding the opinions of a consulting expert — courts have created a minefield of exceptions that may expose experts to broader discovery than a party anticipates.

Disclosure of experts tends to be less strict in arbitration proceedings. Arbitration agreements often limit discovery. They might do so expressly or by requiring adherence to arbitration rules that streamline discovery (such as the JAMS Comprehensive Arbitration Rules & Procedures). 

The JAMS rules require a document exchange and the identification of witnesses, including experts. They require production of “any written expert reports that may be introduced at the Arbitration Hearing” but they do not require experts to prepare reports. The rules also allow the deposition of experts by agreement or for good cause. The absence of an expert report may be good cause for taking the expert’s deposition.

When the agreement is silent, arbitrators control discovery. They generally require document exchanges, but they might not permit depositions or require experts to prepare reports. 

The limited disclosure and discovery rules in arbitration might be an advantage for parties who use expert witnesses. Lawyers may be able to speak more freely with consulting experts. Lawyers may also be more confident that documents prepared by an expert for the expert’s own use will be protected from discovery.

Admissibility of Expert Opinions

In federal court, litigants must satisfy the Daubert standard before an expert witness can testify. Federal judges interpret Daubert inconsistently, making it difficult to predict whether an expert opinion will be admitted.

State courts follow their own standards. They often modify the Daubert or Frye standards or create a hybrid rule. Litigants are challenged to assure that expert testimony fits within a state’s standard of admissibility.

Unless the arbitration agreement imposes a particular standard on the admission of expert testimony, arbitrators are likely to consider the testimony of an expert without considering admissibility of the expert’s opinion. Daubert factors that address the reliability of the expert’s methodology or the sufficiency of the facts that inform the expert’s opinion will generally determine the weight the arbitrator gives to the expert’s opinion rather than the opinion’s admissibility.

Advantages of Expert Testimony in Arbitration

In jury trials, lawyers prepare experts to explain technical language in simplified language. While experts may want to use technical jargon to enhance their credibility, they need to help jurors understand their jargon so that jurors do not become lost in the complex analysis that underlies the expert’s opinion.

Arbitrators are often chosen because they have experience deciding cases within a particular field. An arbitrator who has heard experts testify in similar cases will not necessarily need a “simplified” version of an expert’s reasoning. While jurors who do not understand an expert’s testimony cannot ask for clarification, an arbitrator is free to do so. Arbitration may therefore streamline an expert’s testimony while making it more likely that the decision-maker understands the expert’s opinion.

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What Fees Can Expert Witnesses Charge?

On occasion, expert witnesses agree to work for free. Dr. Martin Tobin, a lung and critical care specialist with more than 40 years of experience, testified that George Floyd died due to a lack of oxygen after Derek Chauvin knelt on Floyd’s neck. Tobin has been compensated for his expert testimony in several civil cases, but he did not charge prosecutors for his expert testimony in Chauvin’s criminal trial.

In some cases, expert witnesses testify as part of their employment. A mechanic who works for an auto repair business might explain why a brake failure that caused an accident was not caused by a faulty repair. In that case, the mechanic is testifying as an expert but will generally be paid only the hourly wage that the employee earns for performing work duties.

In most cases, however, expert witnesses are retained for litigation and promised a fee for their expert assistance. As a general rule, experts are free to set their own fees for acting as a consulting or testifying expert. 

Lawyers, on the other hand, rarely have unlimited budgets. They can only pay fees that their clients can afford. Lawyers are also constrained by rules of professional responsibility that might limit the amount they can pay. Expert witnesses should be aware that lawyers may pay them a reasonable fee but not an exorbitant fee.

Ethical Constraints

The ABA Model Rules of Professional Conduct prohibit lawyers from offering an inducement to a witness that is prohibited by law. For example, a lawyer may not bribe a witness to testify in a particular way. The payment of fact witnesses (as opposed to reimbursing travel expenses) is often regarded as a prohibited inducement to testify.

A comment to that rule makes clear that a lawyer may “compensate an expert witness on terms permitted by law.” Since paying reasonable compensation for an expert’s work is not an unlawful inducement to testify, paying an expert’s fee typically raises no ethical issues.

The rules of professional responsibility in many states address the payment of witnesses more directly. The professional responsibility rules in many states prohibit lawyers from paying more than a “reasonable and customary fee” to expert witnesses.

Reasonable Fees

A fee that the expert has charged in other cases is usually the “customary” fee of an experienced expert. When a witness has given no previous testimony as an expert, a customary fee might be the fee that experts with similar qualifications who are of similar stature charge for their testimony. Fee surveys might provide new experts with guidance as to customary fees charged by expert witnesses in their field.

Unless it is clearly exorbitant, disciplinary boards will generally regard any fee that the expert and the lawyer agree upon at arm’s length as reasonable. The dividing line between a reasonable fee and an exorbitant fee, however, can be difficult to draw.

The issue of reasonableness usually arises when a court requires one party to pay the fee of an expert who testifies for the opposing party. For example, a federal court must require the party taking the deposition of an opposing party’s expert to pay the expert’s reasonable fee for testifying. When permitted by statute, a prevailing party may be able to recover the fees that the party paid to its expert witness.

Federal courts consider several factors when they decide whether the fees charged by an expert witness are reasonable. Those factors include: (1) the expert’s area of expertise; (2) the education and training required to provide the expert insight that is sought; (3) the prevailing rates of other comparably respected available experts; (4) the nature, quality, and complexity of the discovery responses provided; (5) the fee actually being charged to the party that retained the expert; and (6) fees traditionally charged by the expert on related matters.

When both parties employ experts, the court may compare the fees charged by the competing experts as a guide to reasonableness. However, when one expert has stronger credentials or more experience than the other, it isn’t unreasonable for the more qualified expert to charge a higher fee.

The reasonableness of an expert’s fee depends not just on the expert’s hourly rate, but also on the number of hours that the expert bills. Courts generally recognize that an expert must prepare to testify in a deposition. Courts will often agree that it is reasonable for an expert to spend two to three hours preparing for each hour spent testifying.

The time it takes to prepare an expert report is a function of the complexity of the case. When the expert is not required to do extensive research and the facts are simple, the reasonable time to prepare a report will be less than the time required to draft a report in a more complicated case. There is no rule of thumb that helps experts determine the reasonableness of a total fee. As a general rule, if the expert works efficiently and charges a customary hourly rate, the expert’s fee will be reasonable.

Hourly Rate vs. Flat Fee

Most experts charge an hourly rate. Some experts charge a flat fee. Fee agreements might also combine the two forms of payment. An expert might charge an engagement fee that locks in the expert so that the expert cannot be hired by another party. Engagement fees are a fixed sum of money, but they are often treated as retainers. 

An expert who charges an hourly rate might credit a lawyer with an advance payment for the hours covered by an engagement fee. However, experts often require an engagement fee to be nonrefundable, treating the engagement fee as the minimum fee that will be charged for the expert’s work.

Flat fees are often charged per task. For example, an expert might charge a flat rate for each day (or half day) of trial testimony or for each day (or half day) of deposition testimony, regardless of the length of time that the expert testifies. 

Some experts offer services pursuant to a hybrid fee agreement. They charge hourly rates to review documents, meet with lawyers, perform the work needed to reach an opinion, and write a report. They then charge a flat fee to testify.

Contingent Fees

Lawyers cannot pay an expert witness a fee that is contingent upon the trial’s outcome. Even if the lawyer has agreed to accept a contingent fee in a personal injury case, the lawyer cannot enter into a contingent fee agreement with an expert witness.

Courts and the authorities who regulate lawyers fear that expert witnesses will slant their testimony to favor a party if their payment is contingent upon the party obtaining a favorable verdict. Since the court system benefits from honest experts, it disallows contingent fees for the same reason that it prohibits lawyers from paying unreasonable fees. The judicial system discourages any fee arrangement that creates a strong incentive to testify falsely.

What Is the Difference Between a Retained and Non-Retained Expert Witness?

Courts and rule-makers have categorized expert witnesses in ways that can be confusing. Placing an expert witness into the correct category can make the difference between a lawyer’s ability to use an expert at trial and a judge’s decision to exclude the expert’s testimony.

Differing terminology used by state and federal courts contributes to the confusion. Federal courts draw a distinction between retained and non-retained experts. State courts sometimes refer to a non-retained expert as a hybrid witness. In both state and federal courts, the distinction between a fact witness and an expert witness is not always clear. The procedural rules that govern disclosure and expert reports depend on classifying the witness correctly.

Fact Witnesses

Courts generally agree that a fact witness is someone who bases testimony on observation and personal knowledge. Fact witnesses testify about things they perceived. “I saw the blue car cross the centerline and collide with the red car” is fact testimony.

Fact testimony is usually given by lay witnesses, but witnesses who have expertise that does not inform their testimony can also give fact testimony. Whether the witness has specialized knowledge does not affect his or her status as a fact witness. A chemist or an economist who testifies about a car crossing a centerline and causing a collision does not become an expert witness simply because she has an advanced degree.

A jury needs no specialized knowledge to understand the testimony of a fact witness. Since fact witnesses are typically testifying about things that they perceived, fact witnesses do not usually give opinions. An exception to that rule allows lay witnesses to give rational opinions based on common experience if the opinion would help the jury understand the evidence. “He seemed angry,” an opinion based on attitude and tone of voice, is an example of a lay opinion that some courts regard as admissible if the person’s anger is relevant to the case.

Expert Witnesses

An expert witness offers opinions based on the expert’s specialized knowledge, training, or experience rather than the expert’s own perception of facts. An accident reconstruction expert who did not see the blue car cross the centerline and crash into the red car can use the location of debris, gouges in pavement, vehicle damage, and the final resting places of the two vehicles to form the opinion that the blue car crossed the centerline.

Unlike lay witnesses, experts can express opinions if the opinions would help the jury decide an issue that is relevant to the case. Every jurisdiction requires the expert to be qualified to render an opinion. Whether a qualified expert’s relevant testimony is admissible depends upon whether it satisfies the controlling standard in state or federal court. The Daubert standard applies in federal court, while states typically rely on their own version of the Daubert standard, the Frye standard, or a hybrid standard.

The line between an expert and a fact witness can be muddied when an expert discusses facts that are not within the common knowledge of lay jurors. For example, a treating physician will often explain the injuries for which an accident victim was treated. A physician who discusses the significance of a ruptured spleen will probably explain the function of an organ that most people don’t understand.

Courts typically classify treating physicians as fact witnesses, even when their explanation of the facts depends on their specialized knowledge. When a treating physician offers a prognosis, however, the physician is offering an opinion, not stating facts. How to classify a treating physician who offers opinions about the need for future healthcare is a tricky question.

Retained vs. Non-Retained Experts

In federal court, a treating physician who will offer opinions is usually classified as a non-retained expert. A non-retained expert is not hired for the specific purpose of giving expert testimony. A treating physician is hired to treat a patient. Asking that physician to testify about opinions that the physician formed in the course of treating the patient does not make the physician a retained expert because the physician was not retained for that purpose.

As one court explained, a physician is only “retained” if the physician’s testimony is not based on opinions that the physician formed while treating the patient. Thus, a treating physician who expresses an opinion about causation that is based on the physician’s observations has not been retained for the purpose of litigation. On the other hand, a physician who is retained to review medical reports and other evidence regarding a patient the physician did not treat is classified as a retained expert.

While the distinction between retained and non-retained experts usually arises when a treating physician offers an opinion, it can apply to other experts, as well. In the case linked above, the court concluded that the defendant’s former CFO, although hired and paid to offer expert opinions, was a non-retained expert because his testimony was limited to opinions that were based on observations he made while employed by the defendant.

Whether a witness is retained or non-retained is not always clear. For example, when a physician saw a patient only once, three years after an accident, assessed his injuries, and prepared a treatment plan, the absence of any ongoing treatment convinced a court that the physician was retained for the purpose of litigation. The physician offered an opinion as to whether the plaintiff’s injuries were caused in the car accident that was the subject of the litigation or in an earlier car accident. Since the physician formed his opinion by reviewing x-rays taken after the first accident, at a time when the physician was not treating the patient, the physician did not base his causation opinion on observations made in the course of treatment. He was therefore a retained expert.

Why Does the Designation Matter?

In federal court, the Rules of Civil Procedure require disclosure of all testifying experts, whether they are retained or non-retained. The rules governing disclosure of expert opinions, however, are quite different.

Rule 26 requires a retained expert to prepare a written report that includes all opinions the witness will express at trial, the reasons that underlie those opinions, and the facts or data that the witness considered in forming them. Federal courts often bar the testimony of retained experts who write insufficient reports.

Rule 26 does not require a non-retained expert to prepare a report. Instead, the lawyer who plans to call the expert as a witness must disclose the expert’s identity as well as the subject matter of the witness’ testimony and a summary of the facts and opinions to which the expert is expected to testify.

State courts that do not pattern their disclosure requirements on Rule 26 may impose different obligations. State courts sometimes refer to a non-retained expert as a hybrid witness. Whether retained and non-retained (hybrid) witnesses and their opinions must be disclosed, and whether the disclosure requirements differ, is a question lawyers can only answer by reviewing the state’s rules of civil procedure, relevant caselaw, and the court’s scheduling order.

Expert CV Checklist

How to Choose an Expert Witness

Expert witnesses testify in more than half of all civil trials. In state court trials, experts tend to be doctors testifying in personal injury cases. In federal trials, less than half of expert witnesses are medical professionals.

In some cases, the choice of an expert is dictated by circumstances. In personal injury trials, treating physicians may testify as fact witnesses, but they are often in the best position to give expert opinions about a patient’s prognosis and future health care needs.

When parties retain an expert who has no prior knowledge of the case, they may have the opportunity to choose among several potential experts. In a routine case, that choice may be dictated by geography and budget. It might not be cost-effective for a plaintiff in Florida to retain an expert in California. A Florida defendant, on the other hand, might want to create a settlement incentive by retaining a California expert and driving up discovery costs.

Assuming that multiple experts are available who fit within a party’s budget, the choice of an expert depends on several factors. A lawyer’s favorable past experience with an expert might be a decisive factor, but juries may view an expert as the lawyer’s “hired gun” if the same expert testifies repeatedly for the same lawyer.

When choosing among experts who have no prior relationship with the lawyer, intuition can pay a role. Unfortunately, intuition is a less than perfect yardstick for measuring an expert’s likely performance. Lawyers can benefit from research that will inform the lawyer’s choice.

Qualifications

An expert’s credentials and experience are important, but they might only be important as a threshold. Jurors will probably discount the testimony of a witness who clearly isn’t qualified to give an opinion, but jurors do not defer to the opinions of an expert simply because the expert has strong credentials. One study of jury deliberations using mock juries found that jurors consider an expert’s credentials and expertise, but spend the bulk of their time deciding whether the expert’s testimony is accurate. 

The study concluded that credentials are “a peripheral cue” that juries may rely upon to accept an expert’s opinion, “all other things being equal.” The study suggests that jurors scrutinize the quality of an expert’s opinions rather than deferring to the expert’s opinions simply because they come from an authoritative source.

Law Professor Andrew Jurs studied juror perceptions of expert witnesses. Jurs surveyed jurors who had actually deliberated in trials that featured expert testimony. 

Jurs found that an expert’s “impressive academic credentials” were important to 61{d61575bddc780c1d4ab39ab904bf25755f3b8d1434703a303cf443ba00f43fa4} of the surveyed jurors. However, 81{d61575bddc780c1d4ab39ab904bf25755f3b8d1434703a303cf443ba00f43fa4} considered it important that the expert was “a leading expert in the field.”

When Jurs surveyed the experts who testified in those cases, he discovered that experts overvalued academic credentials as a factor that would be important to jurors. Conversely, they undervalued being a “leading expert.”

Lawyers should certainly select experts who are qualified to express opinions, but should not expect jurors to accept an expert’s opinion simply because the expert has strong credentials. If there is evidence that would allow a witness to be characterized as “a leading expert in the field,” however, that expert might be preferable to witnesses who are less prestigious.

Communication Skills

Jurs found that “the most important trait for an expert is the ability to convey technical information in a nontechnical way.” Jurs’ survey revealed that 94{d61575bddc780c1d4ab39ab904bf25755f3b8d1434703a303cf443ba00f43fa4} of jurors valued the expert’s ability to explain testimony in ways that the jurors understood.

Jurs’ finding does not mean that an expert should “dumb down” testimony in a way that jurors will regard as condescending. Jurs cites other studies suggesting that experts enhance their credibility by using technical jargon. The key is to explain jargon using language that jurors can understand.

The research suggests that lawyers should review reports that experts have written in other cases to determine whether the experts were able to convey opinions in a way that laypersons are likely to understand. Assessing an expert’s communication skills, however, goes beyond the expert’s ability to write an accessible report. 

When lawyers interview experts, they should try to get a sense of the expert’s ability to communicate in nontechnical language. Questions like “How do you explain this concept to juries?” will give the lawyer a feel for the expert’s ability to make complex information comprehensible to lay jurors. 

Reviewing transcripts of prior testimony will give the lawyer a sense of whether the expert communicates clearly and whether the witness becomes rattled during cross-examination. Finally, lawyers should talk to other lawyers who have used the expert to get a sense of how effectively the expert is able to communicate technical opinions in nontechnical ways.

Other Factors

The least important of the factors Jurs studied was the expert’s physical appearance. The expert’s “pleasing personality” was also relatively unimportant to jurors. Hiring an attractive and friendly expert is less important than hiring a qualified expert who has strong communication skills.

Most of the jurors told Jurs that they were not concerned about the fees charged by experts. They expected experts to be paid and they did not expert experts to be impartial. Beginning with the premise that experts are likely to be partial to the party that hired them, jurors tended to set aside questions of bias and examined the expert’s opinions on their merits.

According to Jurs, communication is the key to effective expert testimony. A qualified expert who is a skilled communicator will usually be a lawyer’s best choice. 

Expert Witness writing report

What Every Lawyer Needs to Know about Experts Daubert Standard Reports

The Federal Rules of Civil Procedure require experts to prepare a written report if they are retained to testify. State rules may or may not impose the same obligation. Even when state rules do not demand production of a report, a judge’s scheduling order might require a testifying expert to do so.

Lawyers often tell the expert that they need a report, advise the expert of the deadline for its production, and await the result. If an expert has a track record of writing excellent expert reports, further guidance may not be necessary. In most cases, however, a lawyer should remind the expert of the need to describe the expert’s methodology in detail.

The Basics

In federal court, every report must include:

(i) a complete statement of all opinions the witness will express and the basis and reasons for them;

(ii) the facts or data considered by the witness in forming them;

(iii) any exhibits that will be used to summarize or support them;

(iv) the witness’s qualifications, including a list of all publications authored in the previous 10 years;

(v) a list of all other cases in which, during the previous 4 years, the witness testified as an expert at trial or by deposition; and

(vi) a statement of the compensation to be paid for the study and testimony in the case.

Lawyers should make certain to provide an expert witness with a list of the report’s required contents. If the governing state rule differs from the federal rule, lawyers should make sure the expert follows the applicable rule.

Description of Methodology

While the federal rule does not use the word “methodology,” the Daubert decision requires experts to base their opinions on reliable methods. Describing the expert’s methodology — the process by which the expert formed opinions — is an essential part of explaining the “basis and reasons for” each opinion the expert will express.

When judges decide that expert testimony is inadmissible, they usually conclude that the expert report failed to describe a reliable methodology. Experts may take it for granted that they use reasonable methods to arrive at opinions, but the Daubert decision requires experts to “show their work.” 

Experts should provide a step-by-step description of the process by which they formed each opinion. For example, it isn’t enough for an accident reconstruction engineer to write “I examined the accident scene and determined that the defendant’s car was traveling at 80 mph when the collision occurred.” That’s a statement of an opinion, not an explanation of the methodology that produced the opinion.

Instead, the expert should describe the observations she made at the accident scene, including measurements of skid marks, the distances that accident debris traveled from the point of impact, and any other facts that inform her opinion. The expert should then explain the principles of physics that the expert used to make conclusions about the vehicle’s speed. The expert should describe the mathematical calculations that establish the relationship between the facts and the expert’s conclusion about the vehicle’s speed. Describing the process that the expert followed to reach an opinion is usually the most important part of an expert report.

As another example, a vocational expert who assesses future employability should explain the sources of information (including doctor’s reports, the injury victim’s work history and education, and interviews) that inform the expert’s opinions about work limitations. The expert should then describe the method used to assess job availability, including consultation with databases that describe jobs in the economy that a person with the victim’s limitations can perform. The report should cite evidence that those methods are traditionally used by vocational experts to form opinions about employability.

Establishing the Reliability of a Methodology

Supreme Court decisions that address reliability have focused on scientific opinions. They describe factors that scientists have identified as affecting experimental reliability. Have the study results been published and peer reviewed? Have other scientists replicated the results? Was the experiment conducted according to accepted standards? Did the experimental procedure have a known error rate? Is there a consensus within the relevant scientific community concerning the validity of the results of studies that inform an expert’s opinion?

When an expert’s opinion is based on an assessment of scientific studies, the expert establishes reliability by discussing all of the relevant studies, by explaining why some of those studies produced more reliable results than others, and by articulating the reasoning that guided the expert’s acceptance of particular study results. Cherry-picking results that support the expert’s opinion while ignoring less favorable results is not a sign of reliability.

Many experts offer opinions outside the realm of “hard science.” While judicial decisions that focus on scientific opinions do not necessarily fit well with opinions that do not derive from experimental studies, some judges are inflexible in their insistence that experts should always discuss error rates and other reliability factors that simply don’t apply to the expert’s analysis. Experts should take care to explain why their methodologies are reliable, even when the methodologies are not based on an analysis of experimental studies.

For example, an expert in the History of Science provided an expert opinion about the validity of Michael Mann’s climate change studies in Mann’s lawsuit claiming that he was defamed by bloggers. The expert testified that her methodology was “reading and thinking.” The court concluded that “reading and thinking” is not an expert methodology because everyone, including jurors, can read and think.

The expert could have explained that, throughout history, scientists have identified specific methodologies that produce reliable results. She could have identified those scientists and explained why the scientific community embraced the scientific method and rejected alternative means of forming opinions. She could then have explained whether Mann followed the scientific method, comparing his work to the expectations of scientists who have developed and refined that method over the years.

The expert likely had that literature review in mind when she talked about “reading and thinking,” but she didn’t show her work. By condensing the process of evaluating literature into the phrase “reading and thinking,” the expert failed to persuade the judge that she used a reliable methodology to evaluate Mann’s work.

There is little doubt that the expert was qualified to opine about the reliability of Mann’s methods. She likely thought that her own method — identifying the factors that determine reliability and applying those factors to Mann’s research — was self-evident. The court’s rejection of her testimony should be a lesson to lawyers about the need to remind experts that their reports must identify a detailed methodology and must explain why the methodology is reliable.

Courtroom

Screening Experts for Conflicts of Interest and Bias

Lawyers must consider several factors when they choose an expert witness. The expert’s qualifications, reputation, and ability to communicate effectively are key considerations. The expert’s location and the lawyer’s budget are practical issues.

The potential for a conflict of interest is a factor that lawyers tend to forget. Fortunately, actual conflicts are rare. Experts are also challenged when they allegedly show a clear bias for the party that hired them. While those challenges are not usually successful, lawyers need to think about the issue of bias before retaining an expert witness.

Courts are reluctant to disqualify experts based on perceived conflicts or claims of bias. Courts tend to view those issues as going to credibility rather than admissibility. 

Even if a potential conflict does not bar an expert from testifying, lawyers want to hire credible experts. Lawyers need to consider possible challenges to an expert’s credibility based on perceived conflicts or allegations of bias. Screening experts for conflicts and bias should therefore be part of the lawyer’s assessment of potential experts.

Prior Work for an Adverse Party

Courts have the power to exclude an expert’s testimony when the expert has provided services to the opposing party. Courts exercise their power to bar the testimony of an expert who has “switched sides” when they deem it necessary “to protect the integrity of the adversary process, protect privileges that otherwise may be breached, and promote public confidence in the legal system.” 

Whether the expert will be disqualified generally depends on whether the expert received confidential information from the party that is relevant to the current lawsuit. A lawyer’s mental impression of the strengths and weaknesses of relevant claims against that lawyer’s client is an example of confidential information.

When there is a dispute about the expert’s receipt of confidential information, courts ask whether it was reasonable for the adverse party to believe that it had entered into a confidential relationship with the expert. If so, they examine the evidence to decide whether confidential information was actually shared with the expert.

Lawyers need to balance the risk of conflict against the reality that hiring an expert who was once retained by the opposing party may be advantageous. An expert’s willingness to work for both sides might be seen as evidence of the expert’s impartiality. Of course, it might also be seen as evidence that the expert is a “hired gun,” but that is a challenge facing every retained expert in every case.

When an expert has worked for the adverse party, lawyers nevertheless need to be wary. There is always a risk that the opposing party will claim that it shared confidential information with the expert. A lawyer will need to explore the expert’s relationship with the opposing party in detail and will need to assess the risk that the expert might be disqualified. If that risk is significant, the lawyer should consider whether conflict-free experts with similar qualifications are available.

The screening process should start by asking the expert whether she has any past experience with the adverse party or its lawyers. Conducting an online search for cases in which the expert testified will provide at least partial confirmation that the expert has no conflict. Still, since experts do not always testify and since it is difficult to learn of past employment as consulting experts, it is important to have a candid conversation with a potential expert witness about any contact the expert has had with an opposing party, even if the expert did not testify for that party.

Bias

Bias is often alleged by an opposing party. An expert’s consistent employment by a particular industry or group of litigants might give rise to claims of bias, but those claims are attacks on credibility that juries should resolve.

Bias may also be reflected in unreliable methodologies or a selective application of facts. Courts might disqualify experts for bias indirectly by applying the Daubert standard more strictly when there is evidence that bias may have affected the reliability of an expert’s conclusions.

Some courts have suggested that experts who base opinions on experiments or research done outside the context of litigation are more likely to produce reliable results than experts who are hired by a particular industry or group to form opinions that are specific to a lawsuit. After Daubert was remanded to the Ninth Circuit, Judge Kozinski wrote that “experts whose findings flow from existing research are less likely to have been biased toward a particular conclusion by the promise of remuneration; when an expert prepares reports and findings before being hired as a witness, that record will limit the degree to which he can tailor his testimony to serve a party’s interests.” 

That line of thought suggests that courts might be more inclined to exclude experts when they have not conducted research or expressed opinions about a particular subject before they are hired to present expert testimony. Selecting an expert who has researched a scientific question outside the context of litigation might therefore avoid claims of bias.

Still, the fact that an expert has not conducted research prior to being retained does not mean that the expert’s methodology will be tainted by bias. Courts are more likely to be troubled when, for example, an expert prepares peer-reviewed writings and fails to disclose “her potential bias because of her direct involvement in litigation in the . . . cases on which she reported.” 

Experts may also demonstrate bias when they prepare reports that contradict prior writings or testimony given in other cases if the contradictions cannot be explained by the differing facts that the expert considered. To screen against potential claims of bias, lawyers should always review an expert’s past writings and testimony to determine whether it might conflict with opinions the expert will be asked to express.

a 3D printer printing a hand

3D Exhibits May Help Jurors Understand an Expert’s Technical Testimony

Lawyers depend upon expert witnesses to convey their opinions in clear language, breaking down complex ideas into digestible portions that juries and judges can comprehend. While words are an expert witness’ primary tool, juries understand evidence more readily when they can visualize a concept.

Studies suggest that people are more likely to understand new information when it is presented both in narrative and visual form.  Brains process information more effectively when they are stimulated simultaneously though multiple senses, including hearing and seeing.

Demonstrative Evidence

An expert’s visual evidence may be real or demonstrative. Real evidence (also known as physical or evidence) is an object that is material to the litigation. A dented fender with a paint transfer or a fragment of a device that exploded are examples of real evidence. Experts exhibit real evidence to juries while explaining how an examination or study of the evidence caused the expert to form particular opinions.

Demonstrative evidence is a representation of real evidence. Demonstrative evidence depicts a scene, object, or condition as it actually existed. Photographs of an accident scene or an x-ray of a broken bone are examples of demonstrative evidence. Experts use those exhibits to assist their narration of opinions just as they would use real evidence.

Expert witnesses have historically prepared diagrams or drawings to illustrate their testimony. A spinal surgeon might draw a picture of vertebrae to illustrate where an injury occurred, while an accident reconstruction engineer might use a diagram to pinpoint the location of skid marks or debris at an accident scene. 

Because they are familiar to lawyers and courts, diagrams and drawings are usually uncontroversial. The expert will testify that the exhibit accurately depicts the thing it represents and, while the opposing party is free to challenge that testimony on cross-examination, the jury will usually be allowed to see the exhibit if the expert affirms that is a reasonably accurate representation of the facts and if the court finds that it is not misleading or otherwise prejudicial.

Visualization Evidence

Some demonstrative evidence is intended to allow juries to visualize events described by eyewitnesses or deduced by experts. An animation that demonstrates how an accident occurred (or how an expert believes it must have occurred) allows a jury to visualize the accident rather than relying solely on an explanation of a diagram.

As technology has become more sophisticated, so has demonstrative evidence. Three-dimensional visualizations — commonly used by architects to allow a virtual “walk through” of a planned home — allow experts to change the viewer’s perspective so that a scene can be observed from different angles or perspectives. The explosion of 3D printer technology allows experts to build models of objects to exacting specifications.

Like most people, judges tend to resist change. Judges were once wary of technology creeping into the courtroom. Each new generation of judges, however, has been more accepting of technology that has now become commonplace. While judges were once skeptical about animations, most judges now allow experts to illustrate their opinions with animated evidence if the expert authenticates the animation by testifying that it fairly and accurately represents the expert’s conclusions.

3D Evidence and Verdicts

While studies suggest that demonstrative evidence helps juries understand complex testimony, it is less clear whether 3D visualizations are more helpful to juries than photographs as jurors attempt to understand an expert’s testimony. A forensic scientist, a psychologist, and two colleagues designed an experiment to determine the impact that different kinds of visual evidence have on juries.

The authors conducted mock trials before randomly selected individuals who played the role of jurors. They presented evidence to different jurors using three kinds of demonstrative evidence. Testimony established that two men left a tavern together. One of the men fell and died after suffering a serious skull fracture. The question for the jury was whether the victim fell accidentally or was pushed.

A forensic anthropologist testified as an expert witness for the prosecution. The juries heard the same recorded testimony in each trial. The expert used technical language to explain the damage to the victim’s skull.

The experimenters varied the nature of the visual evidence that was shown to the jury as the expert testified. In one set of trials, the jurors saw a photograph of the victim’s skull. In a second set of trials, the jurors viewed a 3D visualization of the same skull. In the third set of trials, the jurors considered a 3D printed model of the skull. The skull was circulated among the jurors, allowing them to touch and examine the exhibit, during the expert’s testimony.

The jurors did not deliberate. Instead, each juror completed questionnaires at the end of the trial. About three-fourths of the jurors who viewed the photograph or the 3D visualization would have returned a “not guilty” verdict, while only 55{d61575bddc780c1d4ab39ab904bf25755f3b8d1434703a303cf443ba00f43fa4} of jurors who saw the 3D printed model would have acquitted.

The experimenters were cautious about attributing significance to the trial outcome as the experiment was not designed to test whether (as other studies have suggested) demonstrative evidence may induce a pro-prosecution outcome in criminal trials. The experimenters did note that jurors who handled the 3D printed model were more likely to conclude that the amount of force required to damage the skull was indicative of guilt. 

Since the expert gave no testimony about the amount of force needed to cause skull trauma, the experimenters suggested that caution should be exercised in allowing jurors to handle 3D printed models of evidence. Perhaps the handling of a skull evoked an emotional response that made jurors more likely to view a defendant as guilty. 

3D Evidence and Comprehension

The experimenters asked whether jurors understood the visual evidence and how the visual evidence helped jurors understand the expert’s testimony. About three-quarters of the jurors found the exhibit itself to be comprehensible, regardless of its nature, although jurors were slightly more likely to understand the 3D printed model.

More importantly, the experimenters found that 79{d61575bddc780c1d4ab39ab904bf25755f3b8d1434703a303cf443ba00f43fa4} of jurors who viewed the photograph thought they understood the expert’s technical language. The use of 3D technology improved the jurors’ understanding of the expert’s jargon. When jurors viewed a 3D visualization of the skull, 88{d61575bddc780c1d4ab39ab904bf25755f3b8d1434703a303cf443ba00f43fa4} of jurors thought they understood the expert’s language. When jurors viewed the 3D printed model, 94{d61575bddc780c1d4ab39ab904bf25755f3b8d1434703a303cf443ba00f43fa4} of jurors said they understood the expert’s technical testimony.

The experimenters suggested that the study might offer evidence that jurors are less likely to misinterpret an expert’s testimony when the experts use 3D reconstructions to explain the terms that they use. The study might also suggest that jurors place greater weight on conclusions they draw from 3D exhibits than they place on conclusions drawn from the expert’s testimony. 

On the whole, the study offered some evidence that 3D exhibits help jurors understand an expert’s technical language. Lawyers may wish to consider 3D exhibits as an alternative to photographic evidence or diagrams if experts feel comfortable using those exhibits to explain their opinions.