The forensic techniques portrayed on crime shows such as "CSI" and "Forensic Files" may not be valid and reliable.
A report recently issued by the President's Council of Advisors on Science and Technology (PCAST) claims that many types of expert testimony provided in criminal trials lacks an adequate scientific basis. The report specifically mentions types of forensic evidence that are frequently used to obtain convictions in criminal cases, such as bite marks, DNA evidence, latent fingerprints, firearm marks, footwear impressions and hair.
The report says that additional research is needed to determine whether certain "feature comparison" methods are scientifically valid. In addition, new objective standards must be established for those forensic methods to be truly useful tools for the criminal justice system.
During the course of its study, PCAST reviewed more than 2,000 scientific papers, and consulted with numerous scientists, criminologists, statisticians, judges, law professors, the FBI and other law enforcement professionals.
Can Forensic Evidence Really Be Trusted?
Perhaps the most startling of PCAST's findings relates to DNA evidence. While the report states that DNA evidence is a reliable methodology, nonetheless as it is currently applied, DNA analysis as it is currently practiced has many shortcomings. For example:
- A re-examination of cases by the FBI found that 11 percent of hair samples identified as coming from the same individual actually came from different individuals.
- 2004 National Research Council report, commissioned by the FBI found that there was an insufficient scientific basis that could enable forensic scientists to draw a definitive connection between two bullets based on their lead composition.
- "Confirmation bias" (the inclination to confirm a suspicion based on grounds other than pure physical evidence), can lead investigators to misidentify and place in custody a suspect
The debate over the validity of certain forensic evidence methods is just beginning. The PCAST report and its implications are bound to lead to continuing and intense controversy among criminologists, law enforcement professionals, and criminal defense attorneys.