|Most video file formats don't save a record of when/how often they are viewed. However, that isn't to say there is no way to tell/estimate. The media player used may keep track of such information, and it may be stored in a separate file or in the Windows registry.|
With that said, my guess would be that you ether misinterpreted what the police said, or they are making things up in an attempt to get a confession.
My advice would be to get a good lawyer who is familiar with cyber-crime, and to not say anything without consulting with the lawyer. If your brother is innocent, and all the police have is a single deleted video, I doubt the case would even go to court.
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