Something happened on your street, a car keyed, a window gone, something worse, and an officer has knocked to ask whether your cameras caught it. This is the moment your CCTV either justifies everything it cost or reveals that it has been decorative for two years. Whether you can help comes down to three unglamorous things: retention, export and timestamps.
Does the footage still exist?
Recorders keep footage until the hard drive fills, then write over the oldest material. Depending on drive size, camera count and quality settings, that loop might be a month or it might be four days, and most owners have never checked which. If the incident was Tuesday and the officer knocks the following Friday, a short loop has already eaten the evidence. So the first move is simple: find the incident in playback and confirm it is there, then stop the recorder overwriting it. Export it promptly, and if you cannot work out how, say so to the officer; forces deal with domestic recorders constantly and would rather help than lose the clip.
Exporting without wrecking it
The wrong way is the common way: filming the screen with a phone. It feels quick and it throws away resolution, frame rate and the metadata that helps footage stand up later. Use the recorder's own export instead, USB stick from an NVR or DVR menu, or a proper download from an app, and export a generous window around the incident rather than a tightly clipped moment; context before and after often matters more than you would guess. Keep the file in its native format even if it needs the recorder's own player software, and hand over a copy while you keep the original. Note who you gave it to and when.
The timestamp problem
Here is the one that quietly ruins cases: the clock. Recorders drift, power cuts reset them, and a system fitted before the last clock change can be an hour out without anyone noticing. Footage of a figure at what the screen says is 02:14 is much weaker if nobody can show the recorder was right. If you discover the clock is off, do not correct it before exporting; tell the officer the offset, since a known error can be worked with and a silently corrected one cannot. Then, once the export is done, set the clock properly, ideally to sync itself from the internet so it stays right.
Being useful before you are asked
Ten minutes of maintenance is what separates helpful households from apologetic ones: check the date on screen this week, find out how many days your drive holds, and do one practice export so the menu is not a mystery under pressure. If the practice run shows a dead drive, a mad clock or cameras too blurry to identify anyone, that is your system telling you it needs attention. There are 335 CCTV system installers listed on this site who fix and upgrade as well as fit; the listings show who covers your area. See installers near you or describe the problem and get quotes. Tonight, though, just check the clock in the corner of the screen. It is the cheapest piece of evidence you own.
