The science that isn't

From Friday's Globe and Mail

For a shocking quote you will never hear on CSI or any other exciting, forensic-based television show, try this: “With the exception of nuclear DNA analysis, no forensic method has been rigorously shown to have the capacity to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source.” The source is not a smooth-talking defence lawyer. It's the National Academy of Sciences in the United States.

The forensic sciences have proved to be frail. DNA evidence has shown up the weaknesses in every other form of forensics: firearms, tool marks (the purportedly unique marks left by an individual screwdriver, for instance), bite marks, shoe impressions, blood spatter, handwriting and hair. Even fingerprints.

This shouldn't be a surprise to anyone who followed the judicial inquiry into Charles Smith, the Ontario child-death investigator whose ineptitude and crusading philosophy helped lead to wrongful accusations and convictions against 20 people. Nor should it be a surprise in the U.S., where a lawyer, Brandon Mayfield, was wrongly jailed for two weeks as a suspect in Madrid's train bombing in 2004, on the basis of the FBI's flawed fingerprint readings.

But for anyone who thought, or hoped, that those were isolated instances, either in Canada or the U.S., the National Academy's two-year study should set them straight. The vaunted science of modern-day forensics has been exposed to little scientific scrutiny. Sometimes what is presented as science is just opinion from someone with questionable training. The scientific investigators may be entangled with the police. And there's little oversight.

Our supposedly skeptical era is infatuated with forensic investigators. TV shows such as CSI: Crime Scene Investigation draw huge audiences. The infatuation manifests itself in courtrooms, too – in the deference shown scientific experts by judges and lawyers, and the weight given their testimony by juries. In a U.S. study of 137 convictions overturned by DNA evidence, 60 per cent included false or misleading analysis of forensic evidence such as blood, hair or bite marks.

The state has an enormous advantage in court when scientific or medical experts testify in support of the prosecution. Most judges lack the scientific expertise to evaluate forensic evidence, the academy notes. Accused people may lack the money to hire experts to challenge the prosecutor's case. They may plead guilty in exchange for a light sentence, as happened in some cases involving Charles Smith. Tammy Marquardt of Toronto said no to a plea bargain, and has been in jail 14 years on a charge of suffocating her two-year-old son. The Supreme Court of Canada has just given permission to reopen her case.

Be skeptical of scientific experts in the courtroom, says the scientific academy. Be very skeptical.