How many movies have Douglas O'Kane and Fred Silverman collaborated on?

They have worked on 21 movies together! Their first movie together was Perry Mason: The Case of the Sinister Spirit (1987) 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 Wicked Wives (1993). They are most known for their crime films together.