No one is arguing that fingerprint evidence has no value. But because it is such a long-established technique, its critics say, it has never been subjected to the rigorous scientific scrutiny necessary to work out how often a bogus match is likely to come up.
What is more, fingerprint examiners occupy a privileged position not enjoyed by most experts. They routinely testify that a print left at the scene of a crime is a definite match to a suspect, with no possibility of error. Indeed the Scientific Working Group on Friction Ridge Analysis, Study and Technology (SWGFAST), which approves standards for fingerprint analysis techniques in North America, has stated: "[Fingerprint] identifications are absolute conclusions. Probable, possible or likely identification are outside the acceptable limits of the science."
But critics such as Cole argue that true science inevitably involves dealing with uncertainty. "The idea that there is something about fingerprints that is fundamentally different from any other area of human knowledge concerns me," says Jim Fraser, president of the UK's Forensic Science Society. "There have to be errors. It is a human process."
Since 1998 there have been legal challenges to at least 40 convictions in the US and UK on the basis of fingerprint evidence, including one last week in the Massachusetts Superior Court. Yet despite this, and the concerns of some experts, the US Department of Justice has so far refused to sanction studies to investigate the reliability of this and other "existing" forensic techniques.
In 1998, the department's research arm, the National Institute of Justice (NIJ), asked for proposals to validate fingerprints. According to Cole, it received four proposals, though none was funded. However, this year's "solicitation" form to attract research proposals, published on 6 January, states that "proposals to evaluate, validate or implement existing forensic technologies ... will not be funded".
In 2003, the US National Academies proposed a research programme to examine the scientific credibility of all existing forensic techniques, from fingerprinting and hair analysis to ballistics and lie detection. But the programme, funded by the DoD and NIJ, fell apart when the sponsors made what were seen by the academics as unreasonable demands to control dissemination and review of the material.
"I think it's censorship," says Paul Giannelli, law professor at Case Western Reserve University in Cleveland, Ohio. He believes US law enforcement authorities should ensure that all forensic techniques are placed on a solid scientific footing, even if that leads to difficulties in the short term.
Anne-Marie Mazza, director of the National Academies' Science, Technology and Law programme, say she is now looking for alternative funding for the project. "I think forensic science should become part of mainstream academic science. It should be peer reviewed, and open science communication is not something to be feared," she says. "Let's be honest, most of these techniques are solid, but there's nothing wrong with trying to find out how solid."
Others put the case for investigation more bluntly. "Various efforts to subject scientific evidence in criminal cases to a rigorous standard of scrutiny have made little progress," says Joe Cecil, a researcher at the Federal Judicial Center in Washington DC.
However, one observer, who asked not to be named, put the government's reticence in a different light. "If all of a sudden, all forensic science is doubted, what happens to all the people in jail. The whole criminal justice system could fall apart."
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