acquit
in
And Then There Were None
(Edited)

to officially find "not guilty" of criminal charges

Being acquitted does not mean the court declared the person innocent. It simply means there was not enough evidence to prove guilt according to the law.

The amount of evidence required depends on the type of case. In a criminal case, where someone could go to prison, the prosecution must prove guilt beyond a reasonable doubt—a very high standard. In a civil case, a lawsuit usually about money, the plaintiff only needs to show that the defendant is responsible more likely than not—a much lower standard.

This is why the same person can be found "not guilty" in a criminal trial (their guilt was not proved beyond a reasonable doubt) but still be found guilty in a civil trial for the same actions (because their guilt was more likely than not).

to handle oneself in a specified way -- which is typically in a positive way

Much less commonly and archaically, acquit can have other meanings. It can mean to release from a duty, as when Jane Austen wrote "I cannot acquit him of that duty" in her novel, Pride and Prejudice.

It can also mean to perform or complete an obligation, as when Charles Dickens wrote "I have a business charge to acquit myself of," in his novel, A Tale of Two Cities.