Matthew "Matt" McGrath is Lita McGrath's son. Andy Barber wanted to speak to Matthew about an incident where Leonard Patz touched him inappropriately. Andy further accused Matthew of having other associations with Leonard, and demanded to know if Matthew knew anything about the case involving his son, Jacob Barber, and the murder of Benjamin Rifkin. This lead to Lita forcing Andy to leave their house.
Sometime later, Matthew called Andy several times, but hung up before he could tell Andy something. After eventually speaking to Andy, Matthew met him at a pizza place. He revealed here, and later at Newton Police Station, that Leonard Patz had approached Matthew and asked if he could touch him inappropriately in exchange for money. This went on for some time until Leonard asked to do it for no money at which point Matthew reported the situation to the police.
Matthew also revealed that Leonard had a fixation with Ben Rifkin when they spoke and after he saw that Jacob had been arrested, he decided to reveal this to the police. Matthew's statement did not convince Neal Loguidice, but it was enough for Lynn Canavan to give a search warrant to Pam Duffy to search Patz's home.