In "Dead Weight" when Columbo arrives at the General's house, he tells the officer to check the yacht and that side of the house. The officer states he needs a warrant, Columbo tells him that he will ask the General permission. Did he ask the General's permission?
He never asked the General, but he told the General that he had done it because he didn't think the General had anything to hide and wouldn't mind.
I'm sure if we over analyze every episode we could find at least one example of something Shady that the lieutenant did. As he stated in Columbo Goes to College, "there's very little that he wouldn't do to solve the case."
Here is a for instance. In Ransom For a Dead mMan, he looks through Mrs. Williams' locker, more specifically at the bag that she had in there. After the money drop.