The Blockchain part is the for the notary part. No one is going to store a video file or the relevant PDF files of sworn testimony on a Blockchain itself, and an S3 bucket is fine of course ; I would have already thought this was extremely obvious.

The notary part is absolutely essential. Renowned Blockchains are the ULTIMATE for this use case. Sorry that you didn't already know this and the other part wasn't already obviously to be assumed by you.

I thought I was posting on a site called Hacker News, I was obviously being too assumptive. I'll spell things out more elaborately in comments in the future.