This achievement is done in the case called "A Slip of the Tongue". It's easily missed because you'd need to catch up with Jean Archer at the Western Union Office near the police station during one of the scripted events in the mission. If you don't reach her in time, you'll miss the chance to interview her, causing you to miss the achievement. You can always replay the case at any time though, so it's technically not a missable achievement.
After the interview session at the used car dealer, you'll receive news that a certain James Belasco is detained in the station for your interrogation. To get this achievement, you must obtain a clue during the Belasco interview, as follow:
Topic: Stolen auto courier - Bad Cop
Topic: Association with Archer - Accuse, show Archer's ownership papers (a clue you obtain during the used car dealer interview)
Topic: Auto theft racket - Bad Cop
Topic: Stolen vehicles warehoused - Bad Cop
You'll obtain the Belasco Ownership Papers clue during the above interview.
Leave the station now, and you'll get two scripted scenes. One from Ray Pinker that gives you two more clues, and another from a patrol who tells you that Jean Archer is spotted at the Western Union Office near your location. You can either run (like mad) or drive there, but make sure you do so as quickly as possible. I reached there in about 30 seconds (real time), and managed to catch up with her. If you don't see anyone at the counter while approaching Western Union, quickly quit and resume before the game autosaves. Do not walk in to talk to the counter people, or you'd have to restart the entire case from scratch.
Once you catch up with Jean Archer, go through the following interview:
Topic: Stolen Kaiser Frazer - Bad Cop
Topic: Association with Belasco - Accuse, show Belasco's ownership papers as evidence
Topic: Stolen auto courier - Bad Cop
Achievement should unlock now.