The fatal police shooting of the unarmed black 18-year-old in Ferguson, Missouri, is prompting calls for more officers to wear so-called body cameras, simple, lapel-mounted gadgets that capture video footage of law enforcement's interactions with the public. In a recent Cambridge University study, the police department in Rialto, California — a city of about 100,000— saw an 89 percent decline in the number of complaints against officers in a yearlong trial using the cameras. The city's public advocate, Letitia James, has called for the cameras as a check on police misconduct following the death of a black man placed in a chokehold by a white police officer last month in Staten Island. The city medical examiner ruled the death a homicide and the Staten Island District Attorney said this week that the case is going to a grand jury. There are privacy concerns for all those being recorded, whether it's the police officers, crime suspects, victims or innocent bystanders. Taser International Inc., which says it is the largest provider of body-mounted cameras to U.S.