Even though body camera's have been effective, some Police departments are now testing Camera's on a Gun to clarify shootings. Associated Press reports that lots of footage was distorted by the Cops body parts or objects when arresting criminals. With a gun camera point of view you will see exactly what the officer is pointing at upon firing and for how long they have pointed the gun at the individual.
Law enforcement officials and civil rights groups are concerned that gun cams do not show the events leading up to the officer pulling out his/her gun. They also won't capture other interactions the officers have with the public. You will only be able to hear audio up until the officer pulls his gun, this will be hard to build evidence skeptics say.