Can security camera or other video evidence count as a witness in Biblical law?
Security camera footage cannot throw stones, which is required of probative witnesses. However, persons who view the footage might commit themselves as witnesses upon the basis of viewing the footage.
Let's say, for example, that a security camera captures a clear, consistent video of the defendant intentionally killing the victim. Could anyone viewing the camera footage act as one of the two probative witnesses required for conviction?
Yes. But the judge -- and anyone volunteering to be a probative witness -- must be convinced that there are no other plausible explanations for the video footage. Video can be faked. Under some circumstances, though, it might be very difficult to fake it.
The persons volunteering as witnesses must confident enough to throw the stone and kill the defendant, based on what they see in the video, because they know beyond a reasonable doubt that the defendant is guilty. Remember, if there is any doubt in the person's mind, then they could end up as murderers (intentionally killing an innocent person).