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.