I think it may be easier to refer to more as a crime tip submission site. However, with that approach you are competing with Crimestoppers which already accepts photos and videos from tipsters. Again, IANAL, but I believe those submissions fall into something similar to a polygraph. Where if you submit a photo/video to the site, the police can use it to build a case, but cannot use it in court.
Depending on where you are located, I do know a few crime scene investigators and computer forensic investigators that I may be able to put you in contact with and who could better answer your questions.
See: https://www.fbi.gov/about-us/lab/forensic-science-communicat...
I'm copy pasting this from their site https://guardtime.com/ksi-technology
* A user interacts with the KSI system by submitting a hash-value of the data to be signed into the KSI infrastructure and is then returned a signature which provides cryptographic proof of the time of signature, integrity of the signed data, as well as attribution of origin i.e. which entity generated the signature.