They're Always Caught is a 1938 short film (20 minutes) directed by Harold S. Bucquet.
It is an installment in the "Crime Does Not Pay" series of shorts produced by MGM in the 1930s and 1940s. In this one the "MGM Crime Reporter" introduces "Dr. John Fisher" (both actors, of course) of the "Scientific Crime Laboratory", who tells a murder story.
The setting is an anonymous American city that is ridden with corruption, graft, and bribery, and organized crime controlled by "Big Matty and the syndicate". Mayor Fletcher, however, is determined to clean up his town, canceling graft-tainted contracts and firing corrupt officials.
Working with the mayor to rid the city of corruption is prosecutor Jimmy Stark—or so it seems. In fact, the prosecutor is in bed with the crime syndicate and is deliberately targeting only small fry while leaving "Big Matty" untouched. Mayor Fletcher has figured this out, however, and confronts Stark, demanding his resignation.
Stark, fearing exposure, assassinates the mayor by means of a car bomb. He gets a huge break when a man who was spotted loitering in the area (he had hoped to speak to the mayor) is arrested. But Dr. Fisher eventually discovers the truth.
- Corrupt Politician: Prosecutor Jimmy Stark is in cahoots with the mob and only pretending to bust the rackets.
- External Combustion: Stark kills Mayor Fletcher by rigging a pipe bomb under the mayor's car, which explodes when the mayor starts his car the next morning.
- Forensic Drama: Possibly the Ur-Example of a work that focuses on a forensic tech solving a case. While the idea of scientific analysis goes at least as far back as Sherlock Holmes and his monograph on cigarette ash, in this short film Dr. Fisher is the protagonist. He analyzes burlap fibers from a sack found under the car, he compares fibers found at the scene to Eddie Fields's pants, and he is able to identify the exact brand of .38 caliber bullet that the bomb was made from by doing a spectrum analysis of the powder traces. Dr. Fisher nails Jimmy Stark by matching the fibers and the powder to fibers and powder found in Stark's hair.
- Framing Device: As with most episodes of this series, the MGM Crime Reporter introduces a law enforcement person who tells the story.
- Protection Racket: Eddie Fields owns a laundry. He is shown paying off one of Big Matty's goons at the exact moment that Jimmy Stark is on the radio announcing that the city's launderers no longer have to pay protection. Eddie's rage at hearing this is what leads him to try to contact the mayor directly, which is how he becomes a murder suspect.
- Reverse Whodunit: We know from the start that Jimmy Stark killed the mayor and the riddle is how Dr. Fisher will catch him.
- Whip Pan: A whip pan takes us from Dr. Fisher in the Framing Device to the main story. A second one takes us back from the main story to Dr. Fisher at the end.
- Writing Indentation Clue: A variation on this as Dr. Fisher uses iodine spray to bring out the impression of the last memo on Mayor Fletcher's memo pad. The uncovered message is "Force Jimmy Stark to resign", which proves to be the big break as Dr. Fisher and the cops then zero in on Stark as their suspect.