Forensic Evidence Is Sometimes Junk Science
A government report finds fault with the use of forensics in court.
Increasingly, law enforcement investigations rely on forensic science, from DNA matching to facial recognition software. Some of the most popular shows on television are crime dramas in which the case is solved by a lock of hair or speck of blood. In real life, many people are unfairly convicted on the basis of sloppy science and flimsy testimony of forensic experts for hire.
The President’s Council of Advisors on Science and Technology (PCAST) recently released a thorough report on forensic science as it is applied in American courts. The researchers identified a credibility gap in the way forensic evidence is collected, tested and portrayed, and in the underlying science of certain forensic methods. To criminal defense lawyers in the trenches, it is hardly shocking that “CSI” prosecutions may be founded on junk science.
A call for better standards
In its report to the Obama administration, PCAST drew two broad conclusions about the current state of forensic criminology:
- There is a need for clarity in scientific standards for validity and reliability of forensic methods. For example, PCAST called out misleading statements in courtroom testimony such as “100 percent certain” or “zero chance” that are not grounded in scientific integrity.
- There is a need to evaluate specific forensic methods to determine whether they have been scientifically established as valid and reliable. Lie detectors are not admissible in court, for good reason. PCAST suggests a need to shore up the methods for comparing DNA, tooth marks, shoe prints, latent fingerprints, ballistics and other physical evidence.
Fingerprints, like snowflakes, are not quite as unique as once believed, and very often police are working with only partial prints. Comparing hair samples, even under a microscope, has been proven unreliable. Bite marks are notoriously inconclusive, but that doesn’t stop forensic orthodontists from declaring a perfect match. The “signature” marks left by the barrel or firing pin of a gun are not as cut-and-dried as TV would have us believe. And so on.
In addition to shaky science and inconsistent lab protocols, the President’s Council said that cognitive bias also muddies the waters. Forensic criminologists do not apply the same rigorous standards as other industries (such as the biomedical community) to ensure objective results. And the PCAST report doesn’t even get into the issue of Fourth Amendment violations and other questionable methods in procuring forensic evidence in the first place.
Justice demands that forensic evidence can be trusted
To be clear, PCAST was commissioned to help federal prosecutors. Government agencies have an interest in making their forensic conclusions more “bulletproof” in court. But citizens also win when forensic science is held to higher professional standards. No one should go to prison when testimony of the government’s expert witnesses is equivalent to forcing a square peg into a round hole.
Source: Forensic Science in Criminal Courts – A Report to the President