in 2003, highlight the sometimes blatant lack of proper education and training of forensic examiners. In the Houston case, several DNA experts went public with accusations that the DNA/Serology Unit of the Houston Police Department Crime Laboratory was performing grossly incompetent work and was presenting findings in a misleading manner designed to unfairly help prosecutors obtain convictions. An audit by the Texas Department of Public Safety confirmed serious inadequacies in the laboratory’s procedures, including “routine failure to run essential scientific controls, failure to take adequate measures to prevent contamination of samples, failure to adequately document work performed and results obtained, and routine failure to follow correct procedures for computing statistical frequencies.”27,28

The Innocence Project has documented instances of both intentional and unintentional laboratory errors that have lead to wrongful convictions, including:

  • In the laboratory—contamination and mislabeling of evidence.

  • In information provided in forensics reports—falsified results (including “drylabbing,” i.e., providing conclusions from tests that were never conducted), and misinterpretation of evidence.

  • In the courtroom—suppression of exculpatory evidence; providing a statistical exaggeration of the results of a test conducted on evidence; and providing false testimony about test results.29

Saks and Koehler have written that the testimony of forensic scientists is one of many problems in criminal cases today.30 They cite the norms of science, which emphasize “methodological rigor, openness, and cautious interpretation of data,” as norms that often are absent from the forensic science disciplines.

Although cases of fraud appear to be rare, perhaps of more concern is the lack of good data on the accuracy of the analyses conducted in forensic science disciplines and the significant potential for bias that is present in some cases. For example, the FBI was accused of bias in the case of the Madrid bombing suspect Brandon Mayfield (see Box 1-1). In that case, the Inspector General of DOJ launched an investigation. The FBI conducted its


Quality Assurance Audit for Forensic DNA and Convicted Offender DNA Databasing Laboratories. An Audit of the Houston Police Department Crime Laboratory-DNA/Serology Section, December 12-13, 2002. Available at


See also M.R. Bromwich. 2007. Final Report of the Independent Investigator for the Houston Police Department Crime Laboratory and Property Room. Available at


The Innocence Project. Available at


Saks and Koehler, op. cit.

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