A screenshot always crops out the message that came right before it.

A screenshot is evidence with borders that somebody chose. What is inside can be completely real and still give you the wrong story, because the sentence that provoked it, the joke it was answering, or the apology two messages later got cut off. Cropping is not always dishonest. It is always a choice somebody made.

Before you pass one along or build an opinion on it, ask what came directly before and after. If you cannot see that, hold your reaction loosely, and be slow to add your name to a pile built on one frame.