Body cameras are no panacea. Although small studies in Rialto, Calif., and Mesa, Ariz., found body cameras can reduce the number of citizen complaints, it's too early to make broad generalizations about the technology's benefits.

So what makes body cameras so attractive? As one Southern California county sheriff put it to me recently, "It's just one more piece of a larger puzzle."

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Think of body cameras as one more tool in the law enforcement toolbox. Often tools have multiple applications. Sometimes tools can be misused. Employed properly, however, the police and the public should benefit from increased transparency and accountability.

But the police unions have been wary at best, and hostile at worst. Unions in Boston, New York, Miami and Los Angeles object to using the cameras without certain ground rules.

The LAPD in December became the largest police department in the nation to begin rolling out the cameras. The police union, which just concluded contract negotiations with the city earlier this month, took the airwaves and newspapers saying that while they favor body cameras, they want a "fair" system.

In a just world where the common good prevails, a "fair" system would ensure the interests of the public trump interests of the public employees' union. In our world, a "fair" system entails protecting union members from the consequences of misconduct or negligence.

What the unions really want is for their departments to let officers review videos after officer-involved shootings or other "critical incidents." Ordinarily, a cop would give a statement on the scene and later submit to a formal interview as part of an internal investigation. The unions argue that officers should have a chance to review footage to help them provide a full account.

In reality, reviewing that footage would also allow officers to shape their testimony to their advantage. Some prosecutors would call that "coaching." And so rather than enhancing law enforcement's credibility, it looks once again like the police are simply protecting their own.

Elected officials, always looking for endorsements, may be tempted to roll over. But for the body-camera experiment to succeed, the police unions must fail.

Ben Boychuk ( is associate editor of the Manhattan Institute's City Journal.