Could fitting police with cameras help stop misconduct and save officers themselves from liability risks? It's an idea that some departments have warmed to, and that some civil liberties activists have tentatively embraced. But turning early experiments into a robust system isn't as simple as issuing cameras along with guns. To help clarify the issues, the ACLU has issued a series of best practices that could point the way forward, offering suggestions for how to record, when to record, and how to address the privacy issues for police and bystanders alike.

Police cameras lie in a difficult place for privacy advocates. Look at it one way, and it's a form of mass surveillance — mobile cameras used at the discretion of an omnipresent security force. Look at it another, and it's more akin to the recordings citizens have made of unlawful arrests. As the ACLU notes, the judge who struck down parts of New York's "stop and frisk" policy suggested police in some precincts be fitted with cameras to improve accountability. But either way, the biggest problem is implementation. Who gets to pick what gets recorded? Should recording be banned in some places? And how long should the recordings be kept?

"If police are free to turn the cameras on and off as they please ... they will no longer become a net benefit."

The first question, for the ACLU, is paramount. "If police are free to turn the cameras on and off as they please, the cameras' role in providing a check and balance against police power will shrink and they will no longer become a net benefit," it says. The simplest solution would be to simply record everything, all the time. But this could hurt both citizens and police who would find every action scrutinized. "Continuous recording might feel as stressful and oppressive in those situations as it would for any employee subject to constant recording by their supervisor," says the ACLU, noting that "shooting the breeze" with a partner or talking precinct politics shouldn't be stifled by surveillance.

One solution, presented by Taser, lets police press a button when they need to record. A small camera catches a 30-second audio-free window before the button was pressed, then starts recording audio and video. To the ACLU, though, that still allows a lot of selective recording, letting police only turn on a camera when it could work in their favor. Barring some futuristic system that could automatically detect when a confrontation was taking place (from, say, raised voices or fast movement) it says the only solution is requiring the police to record every interaction with the public. As an incentive, it suggests restricting the use of evidence from an unrecorded encounter. If an officer is accused of misconduct and hasn't recorded the incident, it could also count against them in an investigation.

Other procedures would govern how citizens could maintain their privacy. Except in cases like raids, they could request that cameras be turned off inside their homes, and police would have to make it clear that they were recording, even if that's as simple as wearing a sticker on a uniform. And only uniformed police should have the cameras. By default, data should be kept for "weeks not years," and anyone should have the right to request video footage of themselves. These policy prescriptions would need to be accompanied by strict technical limits that would keep videos from being tampered with or copied for officers' personal use. If these practices aren't followed, says the ACLU, it will stop supporting police cameras — though the potential impact of that isn't clear.