“WHY DON’T we have footage from body cameras?” asked Betsy Hodges, the mayor of Minneapolis, after a local police officer fatally shot Australian national Justine Damond on July 15. “Why were they not activated? We all want answers to those questions,” she continued. Citizens should want those answers, too.

Ms. Damond, a meditation teacher, called the police to report a possible rape near her home. She called again eight minutes later to report more screaming, and was told officers were on their way. Exactly how that led to her killing is unclear, even though both responding officers were equipped with cameras — because the devices were not turned on. As a result, investigators, citizens and grieving family members are left with fewer answers than they need and deserve.

While the Minneapolis police department has significantly expanded its body camera program in the past year, the tragic shooting of Ms. Damond highlights the gaps still remaining. This month, local television station KSTP found that Minneapolis police officers with body cameras recorded less than 20 minutes of footage for every eight-hour shift — or a total of five or six hours of footage a month. Given that official procedure requires officers to activate their cameras during all traffic stops, searches and encounters involving criminal activity, this figure is much lower than it should be.

A similar pattern emerges across the country. An investigation by the Justice Department discovered that officers in Albuquerque regularly failed to turn on their cameras due to lack of training and oversight. A study of the Denver Police Department found that just a quarter of incidents involving force were recorded. The national figures are even more dire: According to The Post’s database of fatal police shootings, 554 people have been shot and killed by the police this year — but there is body camera footage for just 57 of those encounters.

Although some departments have been slow to adopt the technology due to privacy and cost concerns, evidence suggests that body cameras can serve an important purpose, facilitating accountability and transparency. But unless there is greater enforcement, they will simply be expensive pieces of decoration. In the continuing fallout from the shooting of Ms. Damond, Minneapolis Police Chief Janeé Harteau resigned Friday. That’s fine, but a more systemic response is also needed. Police departments in Minneapolis and elsewhere should consider more expansive training and regular audits to ensure officers are using their cameras appropriately.

Body cameras are no substitute for rigorous training and other policies designed to curb police violence. They can, however, help rebuild trust between law enforcement and communities. They have the potential to be a useful policing tool — but only if officers activate them while policing.