So, I don't have a tremendous amount of knowledge in this area, so I figured it'd be best to seek some advice from you guys

My father-in-law referred his friend to me that needed some data recovered from a computer. Sounds simple at first. Upon further talking with both of them, I found out there is a little bit more to the story.
The guy with the computer (it won't boot; that's all I know.. I haven't seen it) owns his own business and runs it out of his home. The computer in question is used for his business, primarily for shipping and for Amazon stuff. He said there is a possibility that there may also be some family pictures and such on there, and also that is [ex-]wife may have originally purchased this computer, but it has always been primarily for business use.
Well, apparently the wife just decided to take the computer from the house the other day and hand it over to her b/f (supposedly with a little bit of tech knowledge). The guy with the business, got the computer back and since it will not boot.
Any suggestions on this? Should I even attempt to do anything with it? Will he have a case against this guy that supposedly has done something to the computer to cause it not to boot? I just wasn't sure if his first step should be to contact law enforcement or what.
Thanks.
BillV