You are confusing yourself with different issues. Majority courts in this country applying similar rules as federal rules of evidence will have very low hurdle to admit such evidence. To admit the DVD, all you need to do is to authenticate. It does not take much more than a witness, usually the maker or the DVD, to testify that the DVD is what it is, i.e., it accurately reflects what it shows. Best evidence rule will also apply but that is even a lower hurdle to admit such evidence.
Once admitted, how much weight it carries is a jury question and you can provide evidence to refute or prove its alteration.
Once admitted, how much weight it carries is a jury question and you can provide evidence to refute or prove its alteration.