Clifford Spiegelman is a distinguished professor of statistics at Texas A&M, where he has been on faculty for 23 years. He is also a senior research scientist at the Texas Transportation Institute. His applied research interests include chemometrics, transportation statistics, environmetrics, and statistical forensics.
"As currently constructed, however, the practice of forensic science should largely get a no-confidence vote, with the possible exception of DNA evidence (even though the scientific community has yet to be allowed access to the DNA database.) Indeed, Michael Saks and Jonathan Kohler, in a 2005 Science review article, name forensic science testing errors as a contributing factor in 63% of the wrongful convictions in 86 DNA cases studied by the Innocence Project. False or misleading statements by forensic examiners contributed to 27% of the false convictions studied.
The painful truth is that nearly all forensic procedures have been developed without much involvement from the statistical community or enough involvement from the independent, university-based scientific community or federal research labs.
As a result, forensic results are typically stated with uncertainty statements that cannot be supported. For example, it is typical in firearm toolmark identifications to state that, to a practical certainty, the defendant’s gun fired the bullets found in a decedent. Two recent National Research Council (NRC) reports (Strengthening Forensic Science in the United States:A Path Forward and Ballistic Imaging) conclude there is no statistical foundation for such an absolute statement. Also, some federal and state jurisdictions recently ruled that firearm toolmark examiners may only testify that it is more likely than not that the defendant’s gun fired the bullets found in a decedent. (See State of Ohio v. Anderson (pdf) and U.S. v. GLYNN.) That is, the courts require only a better than 50-50 chance of a match."