Expert witnesses are often used by attorneys to analyze facts and circumstances of a case and offer opinions to help jurors better understand the relevant issues. Federal evidentiary rules, which reflect the widely accepted Daubert standard, permit expert opinion testimony providing it is reliable and supported by scientific knowledge. Recently, the Fourth Circuit Court of Appeals issued a ruling that reminds attorneys that an expert’s opinion must also be clearly distinguishable from fact.

Government Witness Improperly Mixed Fact with Expert Opinion

In United States v Garcia, the Federal Fourth Circuit Court of Appeals reversed the criminal conviction of an alleged drug dealer due to improper testimony from an FBI expert witness. During trial, the prosecution relied on an FBI special agent to testify both as a factual witness, based on her work during the criminal investigation, and an expert witness, based on her years of experience decoding drug related conversations. In dismissing the conviction, the Fourth Circuit held “there were inadequate safeguards to protect the jury from conflating [the agent’s] testimony as an expert and fact witness,” reminding attorneys that there must be a clear line between fact and opinion testimony.

In its decision, the Fourth Circuit determined that the Government’s expert witness “moved back and forth between expert and fact testimony with no distinction,” which allowed the prosecution to submit evidence under the guise of expert opinion. For example, the agent testified that the phrase “one hundred forty five point” referred to 145 grams of heroin – a fact she gleaned from the investigation that was presented to the jury as an expert decoding of a drug related conversation. By mixing facts and expert opinion testimony, the prosecution was able to insert evidence into the trial without going through the proper channels.

Improper Connection Drawn Between Facts and Conclusions

The Fourth Circuit also took issue with the prosecution’s drug investigation expert witness for drawing the connection between facts and conclusions – essentially giving the Government’s case additional credence by tying her expert opinion to it. During trial, it is up to the prosecutor to establish facts that are sufficient to convict, and, although experts may opine on the meaning of facts, it is inappropriate for an expert witness to make the prosecution’s argument by connecting evidence to the underlying argument. The Fourth Circuit determined that such testimony falls outside of the evidentiary rule which “contemplates that an expert’s opinion testimony will be ‘helpful to the jury,’ not merely helpful to the prosecutor as transmutations of simple fact testimony.”

Finally, the Government’s FBI expert witness failed to lay an adequate foundation for either her factual or her expert opinion testimony. Under Daubert standards that have been codified by the federal rules of evidence, expert witnesses must demonstrate their testimony is based on reliable, scientific knowledge. This requires attorneys to ask questions during testimony that give the expert the opportunity to support her opinion with reliable methodology or theory. By failing to do this, the prosecution further blurred the lines between fact and expert opinion, and further allowed the FBI expert’s testimony to make the Government’s argument rather than help the jury understand the facts.

Garcia’s Guide for Expert Opinion Testimony

The Garcia opinion clarified that attorneys must be careful when presenting expert opinion testimony. Expert witnesses are permitted to offer their opinion in order to assist the jury in understanding the facts, but an expert cannot be used to tell the party’s story. Expert opinion testimony offers insight into complex issues that jurors may not be able to properly comprehend, but it is up to attorneys to integrate the facts of the case with the expert’s opinion in order to make a convincing argument. As the Fourth Circuit demonstrated in United States v Garcia, judges will hold parties accountable for properly separating expert opinion from fact by dismissing expert testimony that crosses the line between assisting the jury and making the attorney’s argument.