Forensic evidence can provide invaluable information to support a case. However, it is not always trustworthy. In fact, the science behind forensic findings is sometimes dangerously fallible.
As indicated by a report from the President’s Council of Advisors on Science and Technology, many forensic assessments of crime-related items, such as bite marks, hair strands and guns, have too little scientific backing to be considered trustworthy. In short, these under-validated techniques are simply not reliable enough to serve as legal proof, and erroneous convictions could result.
Findings presented by the Federal Bureau of Investigation, the United States Department of Justice, the National Association of Criminal Defense Lawyers and the Innocence Project indicate that errors were found in the expert testimonies of examiners in no less than 90 percent of trials in which microscopic hair analysis was utilized. The examiners exaggerated the importance of their analytical data during their testimonies, giving prosecutors an unfair advantage.
This is a significant problem. The judge and jurors involved in the review of expert scientific evidence may believe the testimonies of the examiners to be incontestable. After all, the scientists are the experts. Nevertheless, even scientists sometimes use questionable methods.
For people who are erroneously convicted, the supporting forensic evidence may be the information that tragically seals their fate. Subsequent DNA testing can reveal some errors. But what happens when a person is wrongly convicted due to faulty evidence and there is no exoneration?
There is a legal framework in which presented scientific evidence is judged, but apparently, this system has been insufficient at weeding out the junk science on which some findings are based. Many of the techniques used during forensic analyses have not yet been deemed scientifically valid.
More research is needed. Structured methods that assess error and accuracy rates in real-world conditions instead of clinical laboratory settings can help provide guiding feedback that backs or discredits examiner testimonies. Until these methods are in place, forensic evidence should be taken with a grain of salt.