I thought that juries are instructed to decided when it's "beyond any reasonable doubt"? So if the defense wants to discredit video evidence they have to make a

I thought that juries are instructed to decided when it's "beyond any reasonable doubt"? So if the defense wants to discredit video evidence they have to make a case that that's a reasonable doubt, probably have experts review the video and provide at least a sketch up of the motive behind spending resources on forging evidence like that. Also I understand that in most cases that go to trial there's more than just video evidence.