Body cameras can have a positive impact. In San Diego, complaints about officers fell 40.5 percent and use of “personal body” force by officers dropped by 46.5 percent after officers adopted body cameras, according to a 2015 report from the city’s police department.

But Professor Stoughton said that as such videos become more commonly used in court to either bolster or dispute the accounts of police officers, people must be careful how they interpret the footage, keeping in mind the cameras’ limits and viewers’ biases.

“People are expecting more of body cameras than the technology will deliver,” Professor Stoughton said. “They expect it to be a broad solution for the problem of police-community relations, when in fact it’s just a tool, and like any tool, there’s a limited value to what it can do.”