Civinfo Hobbyist Trader
Car: 2010 CTS GT
Join Date: 8th May 2013
Location: Cambridge, UK
Thanked 410 Times in 330 Posts
A dash cam does not do a good job of this, especially if you try to use the motion detection feature - the movement has usually finished by the time the camera starts recording.
You could have it recording 24/7, but then you should probably use a separate battery rather than your existing one.
Remember this will still only capture out from one side, so if the car is damaged out of view of the camera you will capture nothing.
You could have multiple cameras, but to get full coverage you would need four.
Your best option is to use a CCTV camera mounted on your house. If this is not possible you can try using a dash cam from within the car, just don't be surprised if the footage is not of much use.