Forensic Laboratory Independence, Control, and Exonerations

The relationship between forensic laboratories and the other institutions of law enforcement varies widely over space and time in the United States. Some jurisdictions have their own local lab within the police or sheriff’s department, others depend on a statewide lab system either independent or under the state police, and others still contract with a private lab to process their forensic evidence. These different organizational forms may shift the incentives lab technicians and managers have to provide timely and accurate analysis and testimony. In this paper, I investigate the relationship between one particular institutional variant, local police/sheriff control of the crime lab, and one particular outcome in the criminal-justice chain: the conviction of innocent defendants due, in part, to faulty or misleading forensic testimony. Among the 200 largest counties in the U.S., counties with locally controlled labs have lower rates of exonerations in which faulty forensics were implicated in the original trial than similarly-situated counties without locally controlled labs that have similar rates of exonerations where forensic problems were not implicated. This difference is robust to state fixed-effects, a variety of observable characteristics, and nearest-neighbor matching. The difference seems to be driven by control, per se, as matched counties containing state-controlled labs have significantly higher exoneration rates.