So You’ve Been Asked to Give an Expert Testimony

By Tanvi Kothari

Forensic scientists play an important role in criminal trials by serving as expert witnesses. Expert witnesses not only testify on the findings but also give opinions based upon the results derived from the analysis of evidence that was collected from the crime scene. These opinions are backed by scientific evidence and forensic science best practices. 

According to the Melendez-Diaz v. Massachusetts decision, the accused has a right to face their accuser, which includes all witnesses presented by the State. This ruling means that forensic scientists now play a crucial role in proof of guilt at trial. Most disciplines of forensics require the scientists to testify on results of their analyses and answer questions relevant to the scope of their field. Testimony is given under oath to the judge and jury selected for the trial.

Here’s how this works from the forensic scientist’s point of view: 

Once the investigating officers submit crime scene evidence to the laboratory, a forensic scientist conducts an analysis and reports the findings to the submitting agency. For example, the forensic scientist would report that the white powder recovered by a police officer at a motor vehicle stop is found to be cocaine, or that the blood stain found on the suspect’s shirt matches the victim’s DNA, or that the testing of blood from a DUI stop confirmed presence of alcohol over legal limit along with presence of controlled dangerous substance (illegal drugs). Upon receipt of the report the suspect can either plead guilty or go to trial.

All people involved in the case can be called to testify as a witness. If a forensic scientist is required for testimony, they would receive a subpoena by the court to testify as an expert witness. A pretrial process can be held if requested by the prosecutor (typically) or the defense attorney. This is the meeting where the attorney and any scientists involved would discuss the findings of the case to understand all details involved in evidence submission, analysis and the return of evidence, as well as going over the report of findings.

During the trial, a forensic expert’s testimony begins with an oath and voir dire. Once qualified to testify, forensic scientists are expected to explain the process of evidence analysis by simplifying technical details so the jury can have a full understanding of the entire process. Direct and cross examinations by the prosecutor and defense attorneys can have a forensic expert on the stand for hours or multiple days, depending on the complexity of analysis.

For some, testifying is an exciting part of their job and for others, it is nerve-racking. Either way, it’s a part of working as a forensic scientist. 

The University of Florida online graduate program prepares graduates for their role as expert witnesses by providing them with a firm understanding of the science behind forensic testing. This allows them to confidently convey the concepts behind their tests to the judge and jury. You can learn more about the program here.