NAS: Bullshit!
The NAS just called “bullshit” on many of the forensic techniques used in labs across the country, ranging from fingerprint, blood splatter, hair, arson and fiber analysis to bullet comparisons. The only technique escaping this harsh critique is DNA analysis, which has been the subject of voluminous study and testing.
The report [executive summary] finds fault with almost all aspects of forensic science: from the lack of standards and scientific scrutiny of “accepted” techniques like bitemarks to a lack of any uniform certification standards.
As a result, there has been little rigorous research to investigate how accurately and reliably many forensic science disciplines can do what they purport to be able to do. In terms of a scientific basis, the disciplines based on biological or chemical analysis, such as toxicology and fiber analysis, generally hold an edge over fields based on subjective interpretation by experts, such as fingerprint and toolmark analysis. And there are variations within the latter group; for example, there is more available research and protocols for fingerprint analysis than for bitemarks.
Lawyers can and have gone to town questioning experts on the “reliability” and “scrutiny” of their methods, but this report provides another powerful tool in exposing (in some instances) the pure speculation of this type of expert evidence:
The report points out the critical need to standardize and clarify the terms used by forensic science experts who testify in court about the results of investigations. The words commonly used — such as “match,” “consistent with,” and “cannot be excluded as the source of” — are not well-defined or used consistently, despite the great impact they have on how juries and judges perceive evidence.
In addition, any testimony stemming from forensic science laboratory reports must clearly describe the limits of the analysis; currently, failure to acknowledge uncertainty in findings is common. The simple reality is that interpretation of forensic evidence is not infallible — quite the contrary, said the committee. Exonerations from DNA testing have shown the potential danger of giving undue weight to evidence and testimony derived from imperfect testing and analysis.
The recommendation is not to “junk” all this science, but rather to develop it and to acknowledge and admit its limitations:
Margaret Berger, a professor at Brooklyn Law School and a member of the panel, explained: “We’re not saying all these disciplines are useless. We’re saying there is a lot of work that needs to be done.”
Said U.S. Court of Appeals Judge Harry Edwards, co-chairman of the panel: “There are a lot of people who are concerned, and they should be concerned. Forensic science is the handmaiden of the legal system. . . . If you claim to be science, you ought to put yourself to the test.”
For more reading, go here, here and here. Scott has his take here.
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about 2 years ago
Hair comparison analysis seems like alchemy.
Plus, isn’t there a push to call plain old expert testimony “forensics” to give it a little more oomph with the jury. Like handwriting analysis–now they’re forensic handwriting analysts. (My view is that they should have the handwriting guy simply lay out the similarities in the two samples and let the jury make a conclusion without his opinion.)
Some of the caselaw is funny when defense attys make Daubert based challenges to hair comparison analysis. In one case, the court threw up its hands and said that there really wasn’t much science, but that there was simply a face to face comparison. See McGrew v. State (Ind. 1997).
about 2 years ago
Besides the government frauds passing their speculation off as “science”, the other question is why would otherwise intelligent jurors ever believe in the scientific reliability of “bite mark” evidence? I am afraid it is because of shows like CSI.
about 2 years ago
I have always worried that the CSI effect has actually been worse for the defense in a way. In part because of what you hit on, that juries are more apt to take as gospel the word of someone who can claim to be like Grissom. I also worry that the CSI effect has made juries accept DNA evidence as proof of guilt, regardless of the context of the DNA. Sort of an “oh, your DNA was at the scene so you must be guilty” thing, even if the presencd of your DNA is in such a place that it really doesn’t have anything to say about who committed the crime.