See also Policing.
Forensic science seems to be a mess, more backed by experience and a history of successful convictions than by rigorous science.
Kaye, D. H. (2009). Trawling DNA databases for partial matches: What is the FBI afraid of? Cornell Journal of Law and Public Policy, 19, 145–171.
The FBI seems strangely resistant to allowing researchers to look through DNA databases to see what fraction of strangers actually do match, to test their random-match probabilities.
Mnookin, J. L. et al. (2011). The need for a research culture in the forensic sciences. UCLA Law Review, 58, 725–779.
“We all firmly agree that the traditional forensic sciences in general, and the pattern identification disciplines, such as fingerprint, firearm, toolmark, and handwriting identification evidence in particular, do not currently possess—and absolutely must develop—a well-established scientific foundation… Sound research, rather than experience, training, and longstanding use, must become the central method by which assertions are justified.”
[To read] Thompson, M. B., Tangen, J. M., & McCarthy, D. J. (2013). Expertise in fingerprint identification. Journal of Forensic Sciences, 58(6), 1519–1530. doi:10.1111/1556-4029.12203