Columbo sets up Halperin but were the other policemen present in on it as well? Lt Duffy who was investigating the robberies was familiar with Artie Jessup, so he must have known where Jessup lived. So as soon they arrived to search Jessup's "home", note that Duffy didn't say this isn't where Jessup lived.

Columbo altered the address in Jessup's file and Columbo says to Halperin himself that Duffy didn't want those files out of his office.

The way the policemen reacted, Duffy and Randall who was with Jessup don't seem stun that Halperin was guilty.

I never thought of it that way, but it makes sense.

Duffy must have known Columbos plans. Probably was told to keep it quiet too. Sergeant Randall is obviously in on it since he brought Jessup to his alleged home. Wonder who took Halperin in......and Mr. Caldwell.

Good point! Never thought of that but you must be right.