What are the circumstances under which your own recordings can be subpoenaed as evidence against you?
I'm not sure if this is what you are asking, but the 5th Amendment protection against self-incrimination applies to testimony, not evidence.
If you possess evidence of a crime, you can be subpoenaed to provide that evidence, even if it incriminates you. Of course you can challenge the subpoena on certain legal grounds too. And it bears mentioning that a subpoena comes after the fact, so by the time you receive a subpoena, you could have already deleted that video in the ordinary course of regular activity. This is why police gather evidence when they see it.
And i think the worry here is that folks would like a nice way to securely delete the information at the scene so that if it is taken as evidence at the time, the evidence is useless.
I'm also not a lawyer, so I could be totally clueless, but I think I'm kinda correct based on what I've seen and heard.