You don't really understand how chain of custody works for digital evidence, do you?
When in possession of a disk image (which is what Rudy has), the image can be verified using a whole image, or even a partition checksum. Any data Rudy or his team finds on his image, can be found on the original drive. Forensics labs don't work with the source disk more than once unless absolutely necessary. They take an image of the disk, and they process copies of the image. This keeps the source material pristine, and as long as the checksums match the original image - it can be proved that the images are true copies.
Hi, I ran the collections and analysis division a computer forensics company for several years. I tried very very hard not to take on criminal cases, because I didn't like seeing shit like what is on Hunter's laptop, and sadly - worse.