I think those issues could be overcome by using encryption and checksums for the logs with the decryption key held by a third party that would read and release

I think those issues could be overcome by using encryption and checksums for the logs with the decryption key held by a third party that would read and release the data on request by the owner or in criminal cases where the owner was a victim. The more likely model is that the insurance companies own and provide the black boxes in return for reduced premiums from the owner. The current situation is that some drivers run their own dashcams and can choose to provide video evidence, but that could be open to abuse if someone very carefully edits the video and no-one spots it. I agree that the drivers shouldn't be forced to self-incriminate - the police should be using their own evidence which could well be from other drivers submitting their own driving data/video.