Jurors’ perceptions of forensic science expert witnesses: Experience, qualifications, testimony style and credibility

The judicial system calls upon expert witnesses to testify in court when complex or specialized knowledge, beyond that of the lay person, is needed to interpret the evidence. Previous research has indicated that particular traits of the expert witness can affect their credibility in the eyes of the jury, however most of this research has been undertaken using mock jurors. In contrast, this study investigated the perceptions of real jurors. In particular, the research focused on the juror's perception of the forensic scientists’ expertise and credibility during testimony in homicide cases. Data was gathered from jurors after nine homicide trials using both questionnaire (n = 29) and direct one to one interviews (n = 22). The jurors defined what they thought an expert witness was and what attributes were important in a forensic scientist. Jurors suggested that the expert witness's education and years of experience were more important than certification or laboratory accreditation. The jurors’ perceptions of the credibility of the expert was based upon the academic qualifications of the expert, the confidence they portrayed in answering the questions ask of them, their demeanor and their status of being government employee. The use of narrative language and demonstrative aids by the forensic science expert witness to explain the evidence was explored. Jurors described a deeper understanding as a result of narrative testimony and this was reported to be a key factor in the juror's acceptance that the witness was credible.