Biased brains

Several items came across the transom today related to my constant meme about the dangers of bias and confirmation bias in investigations and by “forensic” scientists.

First item is a blog at Criminal Law Practitioner, which notes a significant and important change in how photographic line-ups are conducted in Prince Georges County, MD.  This is a potential issue in any number of CID, NCIS, OSI, CGIS, investigations.

On February 9, 2014, the Prince George’s County Police Department (MD) announced that it will start conducting photo lineups using the “double-blind” method.  The new changes will require police officers to institute two safeguards when showing eyewitnesses a photo lineup: (1) police officers must show the witness the photos one at a time, rather than all at once; and (2) the police officer showing the photos must be unfamiliar with the case.  The change is part of an effort to minimize false identifications and subsequently, wrongful convictions.  The accuracy of photo lineups has been a hot topic over the past decade as DNA evidence has been used more frequently to overturn convictions.  A recent study by the innocence project found that eyewitness misidentification plays a role in over 75% of convictions overturned by DNA testing, making it the single greatest cause of wrongful convictions nationwide.

Wrongful Convictions blog alerts us to the work of Itiel Dior.

Here is a link to an interesting piece, “Ignorance is Bliss,” which discusses a potential for confirmation bias in forensic examinations.  This isn’t actually a new topic among legitimate scientists, and relates to the double-blind issue in regard to photo line-ups.

 Dr Dror’s and Dr Hampikian’s experiment presented data from a real case to 17 DNA examiners working in an accredited government laboratory in North America. The case involved a gang rape in the state of Georgia, in which one of the rapists testified against three other suspects in exchange for a lighter sentence, as part of a plea bargain. All three denied involvement, but the two DNA examiners in the original case both found that they could not exclude one of the three from having been involved, based on an analysis of swabs taken from the victim.

As is almost always true in forensic-science laboratories, these examiners knew what the case was about. And their findings were crucial to the outcome because in Georgia, as in many other states, a plea bargain cannot be accepted without corroborating evidence. However, of the 17 examiners Dr Dror and Dr Hampikian approached—who, unlike the original two, knew nothing about the context of the crime—only one thought that the same suspect could not be excluded. Twelve others excluded him, and four abstained.

Though they cannot prove it, Dr Dror and Dr Hampikian suspect the difference in contextual information given to the examiners was the cause of the different results. The original pair may have subliminally interpreted ambiguous information in a way helpful to the prosecution, even though they did not consciously realise what they were doing.

Biased brains, is an interesting piece, about the way police officers and staff examine evidence is always at risk of being far from impartial. Itiel Dror investigates how unconscious human bias can inadvertently influence how scientific evidence is interpreted.

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