True but that's why it's proof beyond a reasonable level of doubt.

I could take strands of your hair and plant them at a crime scene while wearing a high tech containment suit to not leave any of mine.

I could hire actors who are your body double and commit the crime in front of a bunch of witnesses.

Everything is fallible but as video evidence stands a key from a trusted person, who often stands to gain little from giving others access is the most reasonable level of evidence you can provide.

Cctv systems are also a little different in the way they record onto whatever medium they chose that itself has validation methods I am aware of but never had explained.