The ABA House of Delegates approved a Resolution in 2012 urging judges to consider several factors when determining the manner in which expert testimony is presented in criminal trials. The Resolution and its accompanying report urge attorneys and judges to seek “innovative solutions” to help jurors understand the significance and limitations of scientific evidence, such as altering trial structure to allow expert witnesses for both parties to testify consecutively and avoiding declaring a witness to be an expert in front of the jury.
The ABA Resolution and report draw heavily from other ABA standards and from the 2009 NAS Report on the state of forensic science in the United States. More information on the landmark NAS Report can be found here.
The ABA report also critiques trial attorneys’ lack of substantive knowledge regarding scientific evidence and their ability to effectively challenge misleading forensic testimony. “Until an elevation in the knowledge base of trial attorneys is achieved,” the ABA report warns, “the adversarial system will continue to falter with respect to the proper presentation of forensic scientific evidence.”
The ABA Resolution lists several areas of concern for testimony by forensic experts. Highlights include:
Use of Clear and Consistent Terminology
The Resolution urges judges to consider “whether expert witnesses use clear and consistent terminology in presenting their opinions.” The report warns that terms such as “match,” “consistent with,” “similar in all respects tested,” and “cannot be excluded as the source of” have no accepted definition or standardized meaning in the scientific community.
Limitations of Forensic Techniques
The Resolution urges judges to consider whether experts present testimony in a way that accurately conveys any limitations in the forensic techniques they employ. The report points out that experts in disciplines such as microscopic hair analysis sometimes exaggerate the reliability of subjective techniques with misleading phrases like “zero error rate,” claiming that these methods are error-free when performed “correctly.” The report also criticizes the use of phrases with no accepted scientific meaning, such as “reasonable scientific certainty.”
Avoiding Claims of Uniqueness
The Resolution also advocates precluding experts from offering explicit or implied claims of uniqueness unless their findings are supported by empirical research. The report notes that fields such as firearms comparison and handwriting analysis often rely on subjective comparison by analysts with no empirical research to validate their techniques. Testimony by such experts gives jurors an impression that such “matches” represent absolute identification. In particular, the report recommends prohibiting experts from testifying that a match has been made “to the exclusion of all others” unless the experts’ methodology has been validated by empirical statistical research.
Although most judges are unlikely to exclude evidence solely on the basis of the ABA Resolution, attorneys may attempt to use the Resolution to limit the scope and impact of expert testimony in their cases. It isn’t clear how much weight individual judges will give the ABA Resolution, or whether they will interpret the Resolution as placing a higher burden on parties seeking to use expert testimony than already required under North Carolina law. Nevertheless, the Resolution provides strong support for attorneys trying to preclude experts from offering misleading testimony about the significance of their findings, and it calls on judges to monitor the presentation of forensic evidence more closely.