Thats an intrestin example! Is there anywhere a collection of legal cases using timestamps as proof?
Regardless of what we think of immaterial rights especially patents should always make timestamps.
Discussion
I'm not aware of any legal cases where _timestamps_ were publicly used, even though guardtime has been around since forever. My suspicion is that it's good enough evidence that no-one even tries to dispute timestamps.
FWIW, MD5 Hashes are routinely used on electronic discovery platforms to ensure the documents produced/received are the same documents later presented as evidence.
I'd add that it rarely comes up in litigation, but MD5 hashs are often created as a matter of course at the point the document touches the e-discovery platform.