2.3 Case study: The Shirley McKie story
In February 1997, a British policewoman, Shirley McKie, was charged with perjury after testifying at a murder trial that she had not been in the victim’s house, where her thumbprint was supposedly found. McKie’s house was searched and she was taken back to the police station where she was strip-searched and detained because of the controversial thumbprint.
The Scottish Criminal Record Office produced four fingerprint experts who certified that the thumbprint definitely belonged to McKie. However, she maintained her innocence and was acquitted, saved from a potential eight years’ imprisonment, after two American fingerprinting experts endorsed that the thumbprint did not belong to her.
After much media activity, legal action and controversy, Michael Russell, a member of the Scottish parliament, asked fingerprinting experts from around the world to verify the ownership of this thumbprint and had 171 certifications from 18 different countries that the thumbprint did not belong to McKie.
The main concern with the entire issue was not only about its effect on McKie’s career, but also about the accuracy of the Scottish Criminal Record Office’s earlier assertions. A civil trial against the Scottish Executive was due to be heard in early 2006. On the morning of the trial, the Executive offered McKie a settlement of £750,000 without admitting liability. She accepted the offer and the trial did not go ahead. Following the end of legal proceedings, the Scottish Parliament held an inquiry during 2006, which identified fundamental weaknesses in the Scottish fingerprinting service. Before the inquiry reported, the Scottish Criminal Record Office offered early retirement to four of its fingerprint officers, three of whom accepted the offer. The officer who refused early retirement was subsequently sacked, but later won a case for unfair dismissal.
A public inquiry into the case was held in 2009, with the report being published in 2011. The inquiry blamed human error and inadequate procedures for the misidentification of McKie’s thumbprint. It found no evidence of a conspiracy by the police against McKie, nor did it find any weaknesses in the theory of identification using fingerprints. However, it warned:
Practitioners and fact-finders alike require to give due consideration to the limits of the discipline.
Among its recommendations, the inquiry said ‘fingerprint evidence should be recognised as opinion evidence, not fact’ (p. 741).
Shirley McKie received a full personal apology from Strathclyde Police Chief Constable Stephen House in April 2012, more than 14 years after the murder of Marion Ross. Ross’s murder has never been solved.
Based on your current knowledge of digital forensics, what lessons do you think the McKie case has for digital forensic investigations?
Digital evidence can only show what a computer did, not what a person did, and the conclusions of a digital forensics investigators need to distinguish clearly between facts and opinion. It is also important to know what your assumptions are based on. The fingerprint experts assumed that Bertillon’s claim about 16 ridge points making a print unique was true, but it turned out not to be.