Science should decide when violent criminals can walk free

Mental health decisions, and expert opinion, must be based on peer-reviewed science not intuition

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By David Zitner
and Jeff Collins
Atlantic Institute for Market Studies

HALIFAX, NS Jun 11, 2015/ Troy Media/ – Canadians are struggling to find the right balance between ensuring they are safe from people convicted of violent crimes and making sure those convicts are treated ethically.

The dilemma is illustrated by the case of Vince Li, the man who beheaded a fellow bus passenger in Manitoba.

What to do with violent criminals

Li, 39, was travelling on a Greyhound bus, and sat next to 22-year-old Tim McLean. Suddenly, Li killed and decapitated McLean, reporting that voices told him to do it. The court found him not criminally responsible, and sent him to a mental institution. Three years later, many people were appalled when a panel agreed to his occasional release with supervision.

Psychiatrists are stoking the controversy by recommending that Li transfer to a group home and be allowed unescorted outings.

violent criminals
There is no universal agreement on what to do with violent criminals

There is no universal agreement

Meanwhile, in Nova Scotia, André Denny is accused of killing Raymond Taaval, a popular gay activist while on unescorted leave from a hospital after he was found not criminally responsible for a previous assault.

Those who applaud the decision to release Li must believe that psychiatric experts are clairvoyant, and therefore able to predict whether someone who was once violent will not be violent again.

Others believe that violent crime and the limited ability of psychiatrists to predict future dangerous behaviour means that people who have been violent should receive supervision in a secure environment, either a hospital or a jail. They argue that dangerous and chaotic behaviour is too unpredictable to allow re-entry into society.

As one Nova Scotia defence lawyer argued, “Mr. Denny, who committed a violent crime, should not have been granted a one-hour unsupervised leave from the psychiatric facility.”

Mental health workers are as divided on this issue as the public at large. A decision to release or detain violent offenders depends as much on the composition of the panel making the decision as it does on the facts of the case. Unfortunately, the process for deciding fitness to stand trial and the duration of incarceration for violent offenders is capricious and expensive.

More to the story: When the smart guys get it wrong by Pat Murphy

There is no universal agreement in psychiatry. Some psychiatrists may attribute bizarre behaviour to a mental illness. Other psychiatrists, examining the same facts, often reach a different conclusion.

Dr. F.R. Farnham argued in the medical journal Lancet that the forecasting of someone’s level of danger “remains like that of the weather – accurate over a few days, but impotent to state longer term outcomes with any certainty.”

Clinical intuition isn’t adequate to determine who is likely to become violent or why. Consequently, the courts are plagued with conflicting testimony from psychiatrists claiming to be experts, but who rely on subjective opinion not scientific evidence.

Conversely, the key elements for predicting violent behaviour are well known.

Assaults by violent criminals predictable

Peer reviewed work published in the journal Schizophrenia Research states that readily available information allows the prediction of assault. “In a sample of general psychiatric patients with psychosis . . . The information used in the predictive model was: age, sex, having committed an assault in the last two years (self-report) and having used any drug in the last year (self-report).”

Why rely on expensive experts for subjective opinions if objective, scientific information is available to predict someone’s level of danger? In practice, courts resolve psychiatric conflict by asking judges and juries to choose between contradictory opinions.

A quasi-judicial panel with a presiding judge would advance the science behind predictions of danger by insisting that mental health decisions, and expert opinion, must be based on peer-reviewed science. This would rule out the conflicting subjective opinion of people whose sole claim to expertise is that they spent many years in school.

Mercurial medical professionals should not make the final determination for deciding whether to detain violent criminals. Someone with expertise in evidentiary judgment should be part of the process. Let medical professionals offer their opinions on whether detention should be in a hospital or jail.

David Zitner is a family doctor, past director of Medical Informatics at Dalhousie Medical School and the senior fellow in healthcare policy for the Atlantic Institute for Market Studies. Jeff Collins holds a law degree and is pursuing a PhD in political science. He is a research associate with the Atlantic Institute for Market Studies (

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