In the jury room, one of the jurors says that the wife hasn't taken the stand to testify yet. At the end of that scene, the charges have been dropped, so there would have been no more testimony. But when Diane serves the couple later at Cheers, she tells the wife the last time she saw her in court, she was ranting and raving, calling her husband a wife murderer. If the wife never testified, there's little chance she would have spoken in court.
The case on which Diane is serving as foreman ends because "Mrs. Grand is dropping the charges" against her husband. But it is a criminal case, attempted murder, not a civil case. The victim can neither issue nor drop charges in a criminal case.