If they pull away immediately you'll not have solid evidence in the video, but damage to their car might provide that. Sometimes a person will stop momentarily when they hit a parked car, then you will have footage of them in contact and your car moving when they pull away, and that kind of footage is adequate proof. With 'g-sensor' type activation there is a delay, and how long it takes before recording starts is critical. I don't know this cam but with most others that's 2 to 3+ seconds- not good enough.
Phil