Wilko is spot on with his second post re use as evidence. Over the years I've used loads of CCTV as evidence and quite often the clocks maybe out slightly due to issues such as BST and the like. All this has to be taken into account in the witness statement producing the recording. Nothing about accredited installers. Just think about all the dash cams and mobile phone footage that is used these days. Any issues re integrity / admissibility in court would be a matter for the court. Imagine you disturbed a burglar in your house and you had to defend yourself by beating the hell out of him, you bet it would be used in court whether or not it was installed by an accredited person or not.