Private security footage is nothing new to criminal investigations, but two factors are rapidly changing the landscape: huge growth in the number of devices with cameras, and the fact that footage usually lands in a cloud server, rather than on a tape.
When a third party maintains the footage on the cloud, it gives police the ability to seek the images directly from the storage company, rather than from the resident or business owner who controls the recording device. In 2022, the Ring security company, owned by Amazon, admitted that it had provided audio and video from customer doorbells to police without user consent at least 11 times. The company cited “exigent circumstances.”
Probably avoid anything by Hikvision if you don’t want to risk having Chinese backdoors in it. My own system is just a hodgepodge of different used cams I pulled off job sites. Just need to make sure they can do ONVIF and they should be compatible with any NVR out there.
If the cameras are on a private network with no routes to the Internet a backdoor doesn’t really matter. I would still avoid untrustworthy manufacturers.