Another election, another round of blather about crime. More punishment, say the Conservatives. That's how you control crime. No, the Liberals and NDP respond. Prevention and rehabilitation work. Emphasize that. In an ideal world, this would be settled with a thorough review of all available evidence. That world is not ours. In this world, how people judge these claims depends almost entirely on the assumptions they make about human nature. It is common among conservatives to assume that wickedness is inherent in most people, if not all, and threats are the only way to bring them to heel. As punishment increases or decreases so will crime decrease or increase. To conservatives, that just feels right. Liberals tend to have a sunnier view of human nature and so they believe that with the right training and supports, most people, if not all, will behave themselves. More prevention and rehabilitation equals less crime: To liberals, that feels right in the same way more punishment feels right to conservatives. These gut reactions are what politicians go by, and what they appeal to. Which is why they almost never mention evidence. They don't need evidence. They feel the truth. Or rather, they feel what they believe to be the truth. In reality, the politicians are wrong about crime. All of them, across the board. Wrong. The evidence is overwhelming and unequivocal. Major crime trends -the big stuff that makes a real difference -are driven up and down by economics, demography, and other factors we don't fully understand. Prevention, rehabilitation, and punishment may be marginally useful in some circumstances, but they do not, and cannot, determine crime trends -just as health-care systems have only a marginal effect on how long we live. This is not a satisfying conclusion. We like to believe that, for any problem, we can identify the solutions, pull the levers, and have a happy outcome. It's humbling to admit there's lots we don't know. And it's disturbing to acknowledge we're not really in control. But it is reality. This doesn't mean we can do nothing, however. It just means we should be clear about what can and cannot be done. And how it can be done. Marginal improvements are improvements. They should be pursued. But doing that means doing what works, not what we assume will work based on our ideological inclinations. We need research. And we need a willingness to be guided by that research. Prison rehabilitation programs are a classic example. Literally, thousands have been invented since the creation of the modern penitentiary. Do they work? Very often, the answer is "we don't know" because they've never been properly studied. Same for prevention programs. Far too often, they are not subjected to serious analysis. This is indefensible. If we want to drive down crime as best we can, research is essential. So is revision: We must scrap what doesn't work and expand what does. (I should note that the Correctional Service of Canada, which runs federal prisons, is a world leader in research-driven corrections. It's an open question, however, whether it will remain so if the Conservative government continues to push its ideological line.) This may not sound terribly exciting. It is. In fact, taking research and evidence seriously would be revolutionary. In 2001, the National Research Council -one of the world's most prestigious scientific institutions -asked a panel of top-tier researchers to look at the state of research and evidence on illicit drug policy in the United States. "The nation possesses little information about the effectiveness of current drug policy," it concluded, "especially of drug law enforcement." The Canadian research base is, if anything, even thinner than the American. So we are spending huge amounts of money on crime policies whose efficacy is completely unproved. And our political leaders are fine with that, apparently. None of the parties has said anything about this travesty. Unfortunately, that's too typical. The Conservatives have been widely condemned for pushing mandatory-minimum sentences and other punitive policies that will deliver little or no benefit at enormous cost. And justly so. The Conservatives have ignored heaps of evidence. They've even been contemptuous of it. But the Liberals and the NDP have, at various times, supported those policies, or at least them pass in silence. Whether they did so out of sincere conviction or political cowardice, both parties deserve at least some of the criticism that has been heaped on the Conservatives. More broadly, the Liberals and NDP, just as much as the Conservatives, have supported policies they find ideologically or politically congenial without serious regard for evidence. They have not questioned the status quo. They have not demanded more research. They have not put reason and evidence first. They have no reason to be smug. A reality-based crime policy would put a priority on new research. It would commit to scrapping what doesn't work and expanding what does. It would stop fostering the illusion that the criminal justice system determines major crime trends. It would put an end to snake oil.