Not necessarily - there are plenty of references to this topic. Excerpt from one such article follows:-
"If a video is introduced as evidence in a criminal trial in California, the video:
1. must be relevant to the case
2. must demonstrate or prove something about the case
3. must be authentic in a way that can be verified by a video expert
Video surveillance has been a tool of retailers and property owners for decades, but only recently have some criminals started shooting videos of themselves committing crimes, uploading those videos to YouTube or broadcasting live, and even bragging online about their criminal exploits."
Can YouTube Videos Be Used As Evidence?