How many movies have Erle Stanley Gardner and William R. Moses collaborated on?

They have worked on 21 movies together! Their first movie together was Perry Mason: The Case of the Lethal Lesson (1989) while their highest rated movie together was Perry Mason: The Case of the Heartbroken Bride (1992). They have not worked together since Perry Mason: The Case of the Jealous Jokester (1995). They are most known for their crime films together.