The Case of the Haunted Husband - S1-E19
Character mistake: Doris Stephanak tells Perry that a car her friend is accused of stealing had "5,700 miles on the speedometer." She meant "odometer."
Perry Mason (1957)
1 character mistake in The Case of the Haunted Husband
Starring: Raymond Burr, Barbara Hale, Ray Collins, William Hopper
The Case of the Wayward Wife - S3-E13
Revealing mistake: Perry and Della step into an elevator but there is no line in the floor between the floor they are on and the elevator floor. It's continuous.
Hamilton Burger: Incompetent, irrelevant, and immaterial.