Police see it as a waste of time taking most CCTV evidence to court, especially if the perp has a good barrister.
Seems to mostly be used as part of other supporting evidence. Fitted a couple of systems as part of a joint LA/Police scheme in an area, they collected evidence over several months before they would even consider court proceedings.
DIY stuff you may as well save your money, your unlikely to get a clear enough image of anything useful and will certainly not stand up in court.
This tat provides a false sense of security, that may lead to you being less secure.