Police in Ferguson, Mo., got new equipment recently. No, not an M1 Abrams tank — body cameras that record interactions with citizens.

Good idea. Had Officer Darren Wilson been wearing one when he encountered 18-year-old Michael Brown, Ferguson might not have been rocked by angry and sometimes violent protests that captured the attention of the world. It would have been much simpler to determine how Brown’s fatal shooting happened — or the shooting might not have happened at all.

Police cameras, you see, have a way of altering the behavior of both cops and civilians. Both tend to behave better when they know there will be a video record of what they do. One California town found their introduction reduced complaints against police by nearly 90 percent. Police are less likely to brutalize citizens, and citizens are less likely to make false accusations of abuse.

Since the Ferguson shooting, interest in these devices has soared. New York City is putting them on 60 officers in a test. Los Angeles has a pilot underway already. The police chief of Washington, D.C., hopes to introduce them as early as Oct. 1. Police Chief Daniel Oates of Aurora, Colo., whose department uses them and likes them, predicts, “Within five years, every cop in America is going to be wearing a body camera.”

In Chicago, only about 60 percent of squad cars have dashboard cameras. By contrast, all Illinois State Police vehicles have video and audio recording equipment.

But Chicago is ready to dabble with body cameras. The Chicago Police Department will launch a pilot project to equip some officers with wearable recorders. Details are being worked out with police unions and the Cook County state’s attorney’s office.

Why does Chicago need this technology? Consider police Cmdr. Glenn Evans, who has been charged with aggravated battery and official misconduct for allegedly shoving the barrel of his service weapon into the mouth of Rickey Williams, who is now 24. Williams, who has sued Evans and the city, says Evans also put a stun gun to his groin and threatened to kill him.

Had Evans and the other cops present that day been wearing cameras, it would be far easier to establish whether he is innocent or guilty. As it is, it took a lab analysis that found Williams’ DNA on his gun to persuade prosecutors to indict Evans — who had been kept on duty, over the recommendation of a police review board. For that matter, video footage would have come in handy in assessing the 14 citizen complaints against Evans between 2001 and 2006— none of which led to disciplinary action.

If Evans was at fault in those incidents, it would have been valuable to have the evidence to prove that. If he was wrongly accused, it would have been helpful to document that he behaved appropriately. But without video, it’s often hard to be sure.

Losing the Williams lawsuit could be expensive for the city. The Better Government Association says Chicago has averaged more than $50 million a year in settlements, judgments and legal costs in police misconduct cases over the last decade. Money for body cameras is a shrewd investment, bound to save huge sums.

There are privacy issues, of course, in recordings of citizens who may not want the footage to become public. Police departments have to store and archive the material. Police have to resolve if the cameras would be on constantly or could be flipped on only when a stop is made. But minor challenges like these are no reason to reject the technology.

It’s good Chicago is stepping up. The question for the Police Department is no longer, “Why would you equip your officers with body cameras?” It’s, “Why wouldn’t you?”

— Chicago Tribune