Minnesota residents who watch shows like ‘CSI” on television may be surprised to learn that questions have been raised about the validity of forensic evidence and the qualifications of the experts who provide it. After studying the way hairs, fingerprints and fibers are gathered and processed, a panel of scientists, academics and legal experts found problems with virtually every technique and concluded that the interpretation of forensic evidence is often based on subjective factors rather than science. Their findings were published in 2009 by the U.S. National Academy of Sciences.

The NAS report was especially critical of blood pattern analysis. This is a technique forensic experts use to determine the sequence of events at a crime scene based on blood drips, smears and splatter. The NAS experts found little in the way of solid science to back up BPA and discovered that its practitioners often lacked accreditation and proper training. Findings such as these are particularly worrying for groups advocating for criminal justice reform because juries tend to find this kind of evidence extremely convincing.

Other experts have studied the same data and reached similar conclusions. The scientific value of forensic evidence was questioned in a 2016 report released by the President’s Council of Advisors on Science and Technology, and BPA was branded ‘scientifically unsupportable” by the Texas Forensic Science Commission in 2018.

Attorneys with experience in criminal cases may rely on experts of their own to diminish the impact of forensic evidence. Former forensic scientists might cast doubt on the qualifications and experience of prosecution experts, and academics may inform juries about studies that question the scientific rigor of crime scene investigations. Attorneys might also cite these scientific uncertainties during plea negotiations to encourage prosecutors to reduce the charges against their clients in order to avoid the risks of arguing before a jury.