personally I don't tell people I have cameras running, let them dig their own graves
if I had footage that may assist someone else I would where possible just let the person it would help have my contact details for later follow up
Gotcha, I feel the same way. Thinking about possible scenarios, it may be difficult to know who was at fault. I suppose in those cases I would just get the contact information of everyone if I had the time and wasn't in a rush somewhere. If I was rushing somewhere, I would probably resort to calling the police department and letting them know I have footage of a crash.
Edit: I personally would try to provide footage of a crash whenever possible if I got it on camera. A few years ago, I was on a highway heading to church on Sunday afternoon and this car that was about 4 car lengths in front of me goes from doing ~60 mph to slamming on its brakes and coming to a stop for seemingly no reason.
At those speeds, I barely had time to react and so I swerved right/braked to dodge him and went through about 3 lanes of traffic to the right (miraculously without hitting anyone). My 2003 Honda Pilot at the time went spinning (what happens when you slam on your brakes and try to dodge something) like I was playing Mario Kart. I swerved into the right-most lane and eventually dinged a truck (that had actually been behind me in a different lane before I swerved) relatively lightly at ~20 mph.
Air bags went off and the front of my car was crumpled like it had hit a tree. The truck's bumper was pristine compared to my car. It was what you would expect from a fender bender at low speeds. At the time, as a relatively new driver (~2 years after getting my driver's permit), I was confused as to what the hell just happened, but saw out of the corner of my eye, the car that had just caused me to get in an accident drive off sheepishly. You really never forget your first crash and in the moment, the adrenaline makes you wonder what is going on.
Anyways, a good Samaritan a few cars back contacted the police after the crash and sent in the footage. It was not particularly good quality as he was a few cars behind me at an angle, but it showed the car in front of me slamming on its brakes for seemingly no reason (I was not anywhere close to tailgating), and me swerving to avoid ramming him at the highway speed limit (55 mph). It saved me from a wreckless driving charge (in my state, whenever you lose control of you car and it swerves, you are automatically charged with wreckless driving, a criminal misdemeanor that would go on your record).
With the dashcam footage, my lawyer was able to get the charges dropped to a improper lane change which would be comparable to speeding. As I was a male teenager at the time of the accident, people assumed that I was at fault but that dashcam footage really saved me.
We still have that same 2003 Honda Pilot today (though my dad primarily drives it). It is very well possible that my life would be very different today, or I might not be here if things had been different that day. I think that if I had to have a car accident given the circumstances, this was the best possible outcome. I wasn't physically hurt, but it did make me hyper-aware of other drivers who drive like maniacs in the D.C. metro area for a while. I think it's a big reason for why I got my DC dashcam. It really is crazy how your life can end in a few moments while you are driving.
