“Cold Hits” - a new frontier in DNA profiling

The original appearance of this entry was in Danny Weitzner - Open Internet Policy

Last week the Washington DC Court of Appeals ruled (Case no. 05-CO-333, 15 December 2005, Washington, CJ) that it is permissible for the prosecution to use DNA evidence matching DNA collected from a crime scene against a database of DNA samples collected from a large population (in this case, 100,000+ criminal offenders in Virginia). The legal issue in the case on appeal was limited to the question of whether there was sufficient scientific consensus as to method of assessing the statistical reliability of this procedure to justify the introduction of this evidence in court. In particular, the court asked whether there was agreement among experts on how to assess the ‘random match probabiliy,’ the probability that the DNA match identified could have picked out the wrong person. However, the implications of the holding are far reaching in that the path appears to be more clear for matching unidentified DNA found at a crime scene against large database of DNA data.

The underlying case giving rise to the appeal involves the murder of a man in Washington, DC. Initial investigation of the crime yielded a suspect in a related robbery, but failed generate sufficient evidence to charge anyone with murder. In the course of investigating the scene, the police collected blood from the scene and then matched the DNA found in the blood against a database of Virginia criminal offenders. This profiling yielded a ‘cold hit,’ identifying a man named Raymond Jenkins. The trial court, however, refused to allow the prosecution to introduce this match in evidence so the goverment appealed, bringing the case to the Washington, DC Court of Appeals, DC’s highest court. The Court of Appeals determined that the trial court made a mistake in blocking the introduction of the ‘cold hit’ evidence so the case will now go back to the trial court with the government being able to introduce that match against the defendant. As I wrote above, there was no basis for the appeals court to address the larger policy implications of this sort of DNA matching, but this case does mark and important expansion on DNA profililng powers both in DC and likely in the rest of the country.