As I’ve written, most mentally ill people are not violent, and curing all mental illnesses would only prevent a small fraction—about 4 percent—of all violence. However, mentally ill people are more likely to carry out acts of violence if they aren’t being treated—hospitalized or medicated—for their mental illness. In other words, if we do want to prevent the small percentage of mentally ill people who might be violent from being violent, we should try to get them into treatment.

But mental-health advocates say there are many outdated laws and funding gaps that explain why reporting someone who’s acting strangely “to authorities” doesn’t always work to get them treatment. To understand exactly how that breakdown occurs, I spoke with John Snook, the director of the Treatment Advocacy Center, which pushes for more robust mental-health treatment. An edited transcript of our conversation follows.