A more thorough explanation:

Definition: Q.E.D. is a Latin abbreviation for "quod erat demonstrandum," which means "which was to be demonstrated." It is used to indicate that the author has just proven their argument.

Example: In the case of Stupak-Thrall v. U.S., the court stated, "The evidence presented clearly shows that the defendant acted with intent to defraud. Q.E.D." This means that the court has just demonstrated that the defendant intended to commit fraud.

The use of Q.E.D. is common in mathematical proofs and legal arguments. It is used to signal the end of the argument and to show that the author has successfully proven their point.