There seems to be a lot of misunderstanding about snapping pictures in public, especially of police officers while they are eating doughnuts and beating people up....er...working. Police officers will often tell people that it is not lawful to take pictures of police officers when they do their jobs, and will even confiscate cameras of bystanders and arrest journalists and reporters when cameras have clearly caught police officers with their pants down. But the truth is, taking pictures in public is perfectly legal. On private property, one must have permission of the property owner in order to take pictures, but in public, one may snap pictures of anything one can see. Police may not confiscate anyone's camera or SD card without a warrant, and police officers have even been brought up on charges of tampering with evidence for doing just that. The American Civil Liberties Union has published a guide for photographers for reference.
Pictures of police in action, taken by citizens, provide an independent record of the photographed or recorded incident. Such evidence reduces the prevalence of faulty memories and lies, and is important for transparency of those who represent authority. No one should have to worry about police confiscating photographs or cameras, and no police officer should do anything in the line of duty that he or she would not want photographed.