The Lineup - Lineup
Inspector Quine organizes a police lineup for Philip Dressler, the unwitting carrier of the heroin, in the hopes he can identify the porter who had grabbed his bag and flung it into Lefty Jenkins' cab.
Then ... The first group of porters who work for the steamship line that brought Dressler back to San Francisco file in for the lineup.
... in 1961 ... this vintage photo taken 3 years after the movie was released is the actual lineup room (the 'Show-Up Room' in police jargon) in San Francisco's old Hall of Justice. At first sight it looks like the same room, but there are differences that compel CitySleuth to conclude that the movie scene was filmed on a studio set modeled after the real room. Examples of differences - the door is narrower and closer to the corner, 6 1/2 tiles span the wall above the door versus 7 in the movie, the tile grout is dark, not light and the curve on the handrail is a larger radius. Also the fonts on the back-board differ slightly.
Then ... This view shows the whole front width of the room.
... in 1961 ... the actual Show-Up Room is very similar but not identical.
Then ... We get further clues from this view of the rear of the room.
... in 1961 ... clearly, the actual room in the Hall of Justice, below, was different. It was longer, with more benches and an indented rear wall. While it may be that the room was remodeled during those three years it is unlikely given that the Hall of Justice was slated for shutdown and demolition very shortly afterwards. Another explanation could be that there was more than one Show-Up room, again unlikely. So this location was almost certainly a studio set.