It was only six years ago that an inquiry into a slew of baby death investigations botched by pathologist Charles Smith set out to expose the dangers of bad science in Canadian courtrooms once and for all.

At that time, Commissioner Stephen Goudge urged the justice system to insist on better-trained experts and oversight for testing facilities. He also prescribed a healthy dose of skepticism toward the testimony of expert witnesses in criminal cases.

His hopes and recommendations have been ignored. A recent report on the Motherisk scandal at Toronto’s Hospital for Sick Children makes it clear that science has let us down again. The jaw-dropping list of failures documented by Commissioner Susan Lang include mistaken and misrepresented test results, dangerously imprecise testimony and inexplicable shortcomings in peer review and oversight.

It is vital that we waste no time in extracting lessons about a problem that extends far beyond Charles Smith and Motherisk: the justice system’s over-reliance on junk science.

Bad science is an alarming thread that runs through almost two dozen Canadian wrongful murder convictions exposed in recent years by the Association in Defence of the Wrongly Convicted (AIDWYC). The roll call of errors in these cases includes clothing fibres mistakenly believed to match one another; experts who incorrectly concluded that dog bites on a dead child were knife wounds inflicted by her mother; inept autopsies that misinterpreted the cause of death; biology samples contaminated by a government lab technician; and hair samples that anchored a murder conviction, yet later turned out to be worthless.

It is all too easy to latch onto cutting edge science as being a final, perfect answer to our questions. However, the steady evolution in testing techniques ought to serve as a red flag. Arson experts steadily discard old theories about the origin and spread of fire as their science progresses; ballistics technicians evolve new understandings of the impact of bullets on bone or flesh; blood spatter analysts steadily refine their opinions based on new techniques.

In the U.S., the Federal Bureau of Investigation admitted last April that hair identification testimony from its forensic scientists was flawed in 95 per cent of the 268 cases before 2000 it has reviewed so far. In 32 of those cases, the defendant was sentenced to death.

Scientific evidence is tantalizing. It comes with a reassuring aura of reliability. Faced with the messy discrepancies inherent in eyewitness testimony, police reports or wiretap transcripts, judges and juries find comfort in cold, hard numbers and self-assured expertise.

Yet, how is it that we expect our juries to comprehend mind-numbingly complex scientific data or choose between competing experts when very few possess the scientific foundation necessary to make such assessments?

Unlike in television shows, where an investigation and conviction is neatly wrapped up in 60 minutes, forensic evidence is often incomplete and open to interpretation.

Wealthy defendants are able to afford top lawyers and expert witnesses, but indigent accused or those from marginalized communities frequently bear the brunt of bad science evidence. They cannot match cases assembled by well-funded police and prosecutors, sometimes pleading guilty to obtain a reduced sentence in the face of superficially overwhelming evidence.

At precisely the time we ought to be exercising heightened skepticism, a mistaken belief is developing that wrongful convictions are a thing of the past.

It is the exact opposite. The sheen of objective perfection that clings to science evidence in our courtrooms means it must be policed more rigorously. Advocacy groups such as AIDWYC are indispensable and desperately need sustainable funding, as do legal aid programs, which permit determined defence counsel to probe the credentials of forensic laboratories and the opinions of self-professed experts.

Judges must be better trained to weed out junk science and unwarranted opinions offered by experts. And they must warn juries about the perils of placing too much reliance on science or picking sides in a battle of experts.

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Scientific evidence will continue to play an important role in our justice system, but we must continually remind ourselves of its potential pitfalls. As Justice Fred Kaufman noted in his inquiry report on the wrongful conviction of Guy Paul Morin, “an innocent person was convicted of a heinous crime he did not commit. Science helped convict him.”

Daniel Brown is a criminal defence lawyer and a Toronto Director with the Criminal Lawyers’ Association.

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