Wasn't there an episode where a witness in the case, o a friend of a lost person o victim, got married in front of a judge and asked the team (or was it Tiva...?) to be the witness? If so, what episode was it?

It was S11/E20 Page not found. It was Magee and Delilah in the car. They had just dropped off the groom at a courthouse to meet his fiance. The groom was thought to have been dead but had been kidnapped por a bad CIA agent. Delilah and Tim had just decided on a long distance relationship when the groom asked them to be witnesses.That's where that one ended. After Delilah was in w/c, and after Bishop came.