Sometimes scepticism about technology comes from the cops. Earlier this year the Washington Post reported that many small police departments were abandoning body-worn-camera programmes because of the cost. Although the cameras are cheap, officers can generate 15 gigabytes of video per shift; storage costs mount. Police unions often oppose body-worn cameras, fearing they imperil their members by giving superior officers licence to search them for punishable behaviour. Other officers complain about the amount of time required to review and redact footage in response to public-information requests. They also seem not to work. A study from George Mason University released in March found that body-worn cameras had no “statistically significant or consistent effects” on people’s views on police, or on police or civilian behaviour.