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Can a Computer Program Be an Expert Witness?

When DNA testing is too complex for police crime labs, the labs sometimes outsource their testing to a company like Cybergenetics. Most crime labs can handle DNA testing when the DNA to be analyzed comes from one person, but the process is much more complex when DNA from multiple sources has been mixed together.

Cybergenetics has developed a “probabilistic genotyping” software program called TrueAllele. The software uses algorithms that make judgments about how to separate DNA samples in order to create an individual DNA profile for each contributing source.

Computer Programs as Expert Witnesses

According to Cybergenetics, the TrueAllele program is superior to human analysts. Human experts, however, have the capacity to admit that they might be mistaken, particularly when an apparent flaw in their judgment is pointed out in court. The inability to convince a program that it reached an incorrect result is one reason why human experts might be preferable to computer software.

The use of a computer program to provide an expert opinion has sparked a controversy in the criminal justice system. While lab analysts can be cross-examined, it isn’t possible to cross-examine a computer program. In lieu of cross-examining TrueAllele, defense attorneys would like to have their own experts examine the program’s source code to determine whether the program might be flawed. Asserting that the source code is proprietary information, Cybergenetics refuses to release it, making it impossible to determine whether the program actually functions as intended.

The developers of TrueAllele claim that the program removes human bias from the testing process. But perhaps that claim reflects the bias of Cybergenetics, which makes money when outside agencies rely upon the program. Is TrueAllele really more accurate than human experts or is that a marketing claim?

Software Marketing

Cybergenetics offers to conduct a free preliminary analysis for police agencies. If the results show a probable DNA match, the agency can then decide to pay for a full analysis, complete with a report that can be offered as evidence at trial. That model provides an incentive to report a match — without one, Cybergenetics doesn’t get paid.

Cybergenetics’ primary competitor is STRmix, a program developed by a New Zealand-Australia collaboration and marketed by Nichevision in the United States. The FBI uses STRmix. David Balding, a professor of statistical genetics at the University of Melbourne, cites a study in which TrueAllele and STRmix were both used to examine a lab-created sample and returned “significantly different results.” That study suggests that one or both of the programs might be seriously flawed, but which one?

While both Cybergenetics and Nichevision claim that their programs are reliable, the studies that purport to demonstrate their reliability were conducted by the programmers, not by independent testing authorities. The recent White House PCAST report assessing the reliability of expert evidence noted that independent research is needed to verify those claims.

Cybergenetics argues that its internal test results should be sufficient, but Cybergenetics has an economic incentive to produce validation results that will help it sell its services. In the absence of independent testing, why should a court assume that probabilistic genotyping software is reliable?

Admissibility in Court

Courts that have considered whether to admit DNA testing results generated by computer programs have arrived at mixed results. A New York judge disallowed STRmix results in a high-profile case involving the strangulation death of 12-year-old Garrett J. Phillips. An earlier TrueAllele test in that case returned an inconclusive result. The judge decided that the prosecution failed to demonstrate the reliability of the STRmix program.

Other courts have decided to admit the evidence. For example, police officers in Onondaga County, New York stopped a car that was being operated without headlights. The car’s occupants fled into a park and shots were fired. Officers found a gun in the park, but they did not apprehend, and could not identify, any of the car’s occupants.

Police investigators determined that Frank Thomas owned the car. They had no other evidence that tied him to the gun. The local crime lab found the DNA of four to six people on the gun. Because the DNA was mixed, separating it and matching it to a particular suspect was beyond the crime lab’s ability.

The lab sent the samples to Cybergenetics. An analysis by the TrueAllele program computed a very high probability that DNA on the gun matched that of Thomas (or someone related to him). Believing he should not be required to take Cybergenetics’ word for the reliability of its program, Thomas’ lawyer asked for the program’s source code so that an expert could determine whether the program actually works. Cybergenetics refused to provide it and Thomas was convicted of reckless endangerment for firing the handgun. His case is on appeal.

Challenging Computer Software as an Expert Witness

A coding error in the STRmix program affected test results in at least 60 criminal prosecutions in Australia. Whether other errors exist in the source code can’t be determined without analyzing it, but the companies that developed TrueAllele and STRmix refuse to provide their source codes to defense attorneys.

Defense attorneys maintain that convicting defendants on the basis of “secret evidence” is inconsistent with constitutional values that emphasize the importance of cross-examination and disclosure of the basis for expert opinions. Both are fundamental to a fair trial, but it isn’t possible to cross-examine a computer program, and exposing flaws in the program isn’t possible without access to the source code.

Defense attorneys faced with DNA evidence that was produced by software rather than human experts can use their own expert witnesses to point out the inherent uncertainty of test results that cannot be validated by independent, unbiased scientists. Defense attorneys can also challenge the admissibility of evidence that depends upon an unproven methodology and that frustrates the constitutional right to confront a witness. Finally, defense attorneys can continue to demand to have the program’s source code analyzed by their own forensic computer experts.

Until appellate courts begin to recognize and address the problems caused by using software as an expert witness, the admission of probabilistic genotyping test results in a criminal trial will continue to raise serious concerns. As the Electronic Privacy Information Center contends, “Secrecy of the algorithms used to determine guilt or innocence undermines faith in the criminal justice system.”

Pennsylvania Judge Denies Access to Source Code Behind DNA Expert Witness Software

Last year we covered a Pennsylvania legal dispute over DNA testing software used by forensic expert witnesses in criminal trials.  Earlier this week the case took another turn when a Pennsylvania judge blocked defense lawyers from accessing the source code for the software, rejecting arguments that the Sixth Amendment mandated the DNA expert witnesses turn over the details of their methodology.

Defense Attorneys Challenge DNA Expert Witness Software

In Pennsylvania and across the country forensic DNA expert witnesses have increasingly relied on a software program which, according to its creators, is able to improve the accuracy of DNA testing significantly.  The program, called TrueAllele, can provide police investigators and prosecutors with a positive match using DNA found at a crime scene by comparing it to large databases of stored genetic material.  Experts analyze genetic material using the TrueAllele program in order to single out individuals who are linked to the crime, and it has been used in sexual assault, homicide, and property destruction criminal trials.

Pennsylvania and several other states have widely adopted expert witness use of TrueAllele with several police departments and trial courts fully integrating the program.  The program has gained favor because of its ability to parse out individual DNA from multiple sources, which is a feature most crime labs are unable to accommodate.  TrueAllele’s DNA analysis is more thorough than competing tools, giving investigators better opportunity to single out suspects.  Despite the software’s growing acceptance in the legal system, defense attorneys in Pennsylvania have resisted its continued use because they are unable to gain access to TrueAllele’s source code.

Defense Attorneys Petition to Access TrueAllele’s Source Code

Defense attorneys for Michael Robinson, a man charged with shooting and killing two men in Allegheny, PA, argued that the hidden source code behind TrueAllele denied their client the opportunity to adequately confront all of the evidence against him.  Robinson’s attorneys, like others before them, argued that the mysterious software program may provide DNA results which police and prosecutors find useful, but its reliability and accuracy cannot be adequately tested without other experts fully analyzing the code which the program uses to parse out genetic material.

TrueAllele has not been in circulation for very long, and defense attorneys claim that without verification by independent experts there are too many unanswered questions about its accuracy to trust.  DNA evidence, which is heavily used in criminal trials, was the center of a scandal last May when the FBI admitted to providing inaccurate expert witness testimony at hundreds of trials due to faulty tools of analysis, and defense attorneys have shown a hesitancy to accept forensic analysis technology at face value.

TureAllele’s creator, computer scientist Mark Perlin, has consistently resisted sharing his source code by arguing it would be economically disadvantageous for his company to do so.  Currently Mr. Perlin’s company Cybergenetics is the only one using the software, and he does not want to disclose trade secrets as part of a criminal trial.

Pennsylvania Judge Protects DNA Software Source Code

In response to requests by attorneys for Michael Robinson who requested the TrueAllele source code be revealed as part of their cross-examination of prosecutor DNA expert witnesses, Judge Jill E. Rangos said the defense did not sufficiently demonstrate the need for the source code.  According to Judge Rangos, requiring Cybergenetics to disclose the source code has “the potential to cause great harm” because of it is a highly valuable trade secret which no other company is able to duplicate at this time.  Further, Judge Rangos said that revealing the source code is not “the lynchpin to undermining the Commonwealth’s case” against Robinson, and therefore the defense does not have sufficient reason to put Mr. Perlin’s business at risk by exposing his code.

Robinson’s defense team publically disagreed with the ruling, maintaining that defendants have a 6th Amendment right to adequately confront witnesses, and in this case that means challenging the foundation of the technology used by expert witnesses who provide DNA testimony.  Perlin maintains that experts do not even use the source code, but simply rely on the technology to produce a result after they input data and attorneys can safely test the extent of the expert’s knowledge and methodology without access to the underlying code of the software.

Judge Rangos’s ruling echoes the result from a handful of other criminal courts across Pennsylvania and other states, so for now DNA expert witnesses can safely use TrueAllele without Cybergenetics revealing the protected source code.

Technology Used by DNA Expert Witnesses Faces Scrutiny from Defense Attorneys

Law-enforcement and defense attorneys in Pennsylvania have engaged in a legal battle over technology used by DNA expert witnesses to narrow down suspects and identify criminal defendants.  Use of a computer program which unravels DNA inter-mixed at crime scenes has been disputed by defense lawyers who do not have access to its programming source code.

DNA Experts in Pennsylvania use High Tech Program

Over the last few years technology has emerged which allows law-enforcement officials to parse through mixed DNA samples taken from crime scenes in order to positively identify a single suspect.  TrueAllele, developed by the Pittsburgh-based company Cybergenetics, is able to infer a genetic profile from DNA and match it with large databases in order to provide police and prosecutors with positive matches.  According to the TrueAllele website, the technology reduces the chances of misidentification, operates without bias against certain suspects, and meets all legal and scientific guidelines for reliability.

The software is billed as a DNA identification tool for use by police investigating sexual assault, homicide, property crimes, and mass disasters.  In each case the TrueAllele software is able to single out “major and minor contributors” to the incident with the goal of assisting law-enforcement in identifying, arresting, and prosecuting parties responsible for criminal activity.  TrueAllele has been widely used in at least six states across the country including New York and Pennsylvania, but recently defense attorneys have pushed back against the software because expert witnesses who use it are unable to provide details about how the program works.

TrueAllele DNA Identification Software Challenged by Defense Attorneys

Defense attorneys who have been involved in cases where TrueAllele was used to connect defendants to a crime argue that secrecy surrounding the software combined with its impact on jurors violates suspect’s constitutional right to be considered innocent until proven guilty.  Citing a phenomenon known as the “CSI effect” concerned defense attorneys point out jurors not only expect scientific evidence, but place heavy reliance on it when making final verdict decisions.  The impact of DNA expert witnesses using TrueAllele on trials is significant, and with the software’s creators refusing to provide defense attorneys with the source code some attorneys questioning the legitimacy of the program’s use in criminal cases.

According to TrueAllele creator Mark Perlin, the program’s source code is a protected trade secret, but defense attorneys should be satisfied with its validity because of the software’s repeated use in trials to both identify guilty subjects and exculpate innocent ones.  Additionally TrueAllele has survived intense peer-review scrutiny by top DNA and computer program experts who attest to the software’s ability at accurately identifying DNA matches when crime scenes contain samples which make identifying one individual difficult.

Defense attorneys are not convinced, however, and argue the risk of miscodes or inaccuracies in TrueAllele’s source code can result in false convictions of innocent defendants.  Without access to the underlying code in a program DNA expert witnesses are citing to positively make matches that jurors will heavily rely on in their verdict decision, defendants arguably are not given a fair opportunity to challenge the evidence presented against them.

DNA Expert Witness Software Faces Legal Challenge

Defense attorneys for a man accused of murder in Pennsylvania have challenged the admissibility of TrueAllele evidence presented by a DNA expert witness by arguing the validity and methodology of the measure cannot be verified without access to the underlying source code.  Suspicion surrounding TrueAllele is driven by an announcement by the FBI in May that work done by forensic expert witnesses working for the agency on thousands of cases may be inaccurate due to faulty DNA identification software.  With the integrity of thousands of convictions at risk due to errors in DNA matching, defense attorneys are understandably suspicious of a software program with source code they cannot independently verify.

Despite the arguments against the use of DNA experts using TrueAllele, the software has been accepted in a number of criminal trials as reliable and scientifically valid evidence for expert witnesses to use when explaining forensic analysis to jurors.  TrueAllele has a short history, but its gaining acceptance indicates the software has been vetted more thoroughly than the programs which created errors for FBI expert witnesses.  Whether or not defense attorneys gain access to the source code, the use of TrueAllele by DNA expert witnesses seems likely to expand as trials increasingly rely on forensic analysis for reliable evidence.