Other mistake: In the home of a murder victim, Columbo presses the telephone's "redial" button to see who was called most recently. A seven-digit number is displayed but only six beeps are heard as the number is redialed. Later, attorney Oscar Finch places a call by dialing only five numbers.
Other mistake: Archie goes out to the outside front porch to paint it. At the end of every show, the house they show doesn't have an outside front porch.