Mason Clark was the husband of murderer and serial rapist Jeremy Jones. When Jones would find gay men at bars to rape and rob, Clark would be gifted with the men's jewelry. This would be mixed with Jones' abuse and lies toward Clark.
When Jones was arrested and put on trial, Clark was in disbelief and stood in his defense. But when he found out the truth about the jewelry and the widow of the man Jones murdered convinced him, Clark turned in the evidence. Jones snapped at Clark with slurs and spat at his counsel before being removed form the court room.
Clark most likely got a divorce from Jones after his imprisonment. (SVU: "Criminal Hatred")