On a good day, with an excellent print and the best people doing the matching you can be pretty sure if this print is from this person, but crime scenes are not that perfect scenario and the actual crime scene investigator might be less than great at the matching or influenced to some extent by what their boss wants.

There's a big difference between "This thumbprint in blood was on the recovered murder weapon and it's a perfect match" and "This smudge of half a finger on a paper bag found near the scene was arguably a match" but the jury isn't necessarily told about this and where on that scale the evidence they've been told about would lie.