Civil liberties advocates said they expected the failure of body cameras worn by two Baton Rogue police officers when they shot dead a black man to be part of a federal investigation into the latest U.S. shooting to spark protests over the use of excessive force by police. The cameras, intended as a major deterrent to police shootings because of the documentation they could provide, were knocked out of position during the altercation with 37-year-old Alton Sterling resulting in poor-quality video, police revealed on Wednesday. Police officials did not say which company made the cameras worn by the officers who killed Sterling, where they were located on their uniforms or how they were knocked loose, but civil rights advocates said they expected a U.S. Department of Justice investigation to answer those questions. "How could that possibly happen?" asked Marjorie Esman, executive director of the American Civil Liberties Union of Louisiana in a telephone interview on Wednesday, a day after the shooting. "I assume the Justice Department is going to look at absolutely everything, which would have to include what happened with the cameras." Baton Rouge is transitioning from using cameras made by L-3 Communications Holdings Inc to those made by Taser International Inc, according to Taser and local media reports. A Taser spokesman said his company's cameras were not involved in the incident and an L-3 spokesman declined to comment. Baton Rouge police officials did not respond to a request for further comment. Law enforcement experts said it was rare for such cameras to fail but not unheard of in a case where an officer is wrestling with someone. Taser's body-worn cameras are secured with high-powered magnets and require the user to hold a power button down for five seconds to turn them off, a design intended to discourage officers from turning them off during confrontations. Over the past year police departments in major U.S. cities including Los Angeles, Chicago, Detroit and Baltimore have begun equipping their officers with body cameras or seeking funding for them. Some 95 percent of police departments intend to adopt them, according to a December survey conducted jointly by the Major Cities Chiefs Association and Major County Sheriffs Association. "Body cameras are a step forward in most people's minds, but they are not the silver bullet that people believe they might be," said Darrel Stephens, executive director of the Major Cities Chiefs Association. "I can see that people might be skeptical of that but those things happen."