Problems with forensics, including bias affecting DNA testimony

[NancyLebovitz]

Forensic Science and the Innocence Project

What’s more, some types of DNA technology have shortcomings, as Boise State University geneticist Greg Hampikian cautioned Philadelphia meeting attendees. Sample collection methods haven’t changed since DNA’s courtroom debut in the 1980s, even though assay sensitivity has increased dramatically, he said. His group has shown that detectable amounts of DNA can transfer between specimens if a handler forgets to change gloves. Hampikian, director of an Innocence Project affiliate in Idaho, also showed that if exposed to extraneous details about a case, experts can give very different interpretations when analyzing DNA mixtures, as can appear in cases of gang rape Sci. Justice, DOI: 10.1016/​j.scijus.2011.08.004. Despite these caveats, DNA testing is the gold standard among forensic disciplines, because it has undergone thorough scientific vetting.

Unfortunately, Sci.Justice study is behind a pay wall.

[VincentYu]

Unfortunately, Sci.Justice study is behind a pay wall.

Here it is.

Abstract:

The objectivity of forensic science decision making has received increased attention and scrutiny. However, there are only a few published studies experimentally addressing the potential for contextual bias. Because of the esteem of DNA evidence, it is important to study and assess the impact of subjectivity and bias on DNA mixture interpretation. The study reported here presents empirical data suggesting that DNA mixture interpretation is subjective. When 17 North American expert DNA examiners were asked for their interpretation of data from an adjudicated criminal case in that jurisdiction, they produced inconsistent interpretations. Furthermore, the majority of ‘context free’ experts disagreed with the laboratory’s pre-trial conclusions, suggesting that the extraneous context of the criminal case may have influenced the interpretation of the DNA evidence, thereby showing a biasing effect of contextual information in DNA mixture interpretation.