For a legal situation you probably should have a calibrated meter which rules out the i-phone, radio shack meter and most other over the counter meters, those are good for rough approximations, but if something needs to stand up in court, I'd suggest you should get with a professional acoustician, who can probably give even a better measurement than LEO's can, its one of those deals- like with Radar, if it is calibrated recently it's pretty strong evidence, if it's been a while, or if it hasn't been calibrated- it becomes questionable.