Involuntary Suicide Mechanism

An espionage/science fiction trope, this is where agents/those who know important information are wired so that if they are interrogated, they will die instead of divulging any information. Generally a sign of having a Bad Boss who doesn't care about the lives of his subordinates, although at least in theory, it could be a somewhat humane way of allowing the captured agent to escape some amount of torture. Compare with Cyanide Pill which is more "voluntary" and the related concept of the Explosive Leash.

Comic Books

 * Judge Dredd: Mega City One Blitzers are hitmen with implanted explosives wired to detonate with the stress of capture.
 * Watchmen has a lowtech version of this, where Veidt pretends to be stopping a would-be assassin  from taking a Cyanide Pill,

Literature

 * Actors in The Acts of Caine are conditioned so that they cannot (on Overworld) admit they are Actors, speak Earth languages, etc. Approaching the topic can give them fits. They will die before they can say it.
 * In Battlefield Earth, the sinister cabal of psychiatrists that rules the Psychlo race has implanted mind-control devices in their subjects' skulls, both to modify behavior and protect the all-important secret of teleportation. If an alien asks a Psychlo about teleportation or even mathematics, males are conditioned to go into a suicidal killing spree, while females go catatonic.
 * In the Onyx Court book Midnight Never Come, Invidiana has put a spell on Tiresias that will kill him if he tells what he knows about her.
 * Happens to one of the Grey Men in The Stainless Steel Rat's Revenge.
 * Star Wars: There's a fairly complicated version of this in the X-wing Rogue Squadron novels by Stackpole. There's a drug called skirtopanol that is used in interrogating prisoners, since it lowers their defenses and makes them more sensitive to pain. But if someone's been taking lotiramine, the chemicals react, sometimes fatally. An Imperial gave lotiramine to someone he'd used, telling the man that it would protect him from a plague that was going around. When the local Complete Monster caught up with the Imperial, he told him that the man had gone into convulsions and died after being dosed with skirtopanol. The Imperial was surprised. He'd have had to have been taking four times the recommended dosage to go into convulsions.
 * In The Stars My Destination, the crew of the Vorga was implanted with a mechanism that would stop their hearts if they started to give information revealing the circumstances explaining why they passed by the protagonist, Gully Foyle. When Foyle starts torturing the first of the crew members, he dies the moment he starts divulging information.
 * After the second time this happens Foyle gets annoyed. Using the illegal Bullet Time reflexes he paid for he knocks out his third target, cuts out his heart and connects his circulatory system to an artificial blood pump within twenty seconds. Then he starts questioning him.
 * In the Tortall Universe, a death spell can be used for this purpose. It doesn't save the victim from torture/TruthSerum interrogation, but it kills him if he tries to give up accurate information. Aly comments to a captured spy that "if someone put three death spells on me, I'd wonder whether they trusted me at all".
 * In the Vorkosigan Saga series, Imperial Security agents are doctored so that they will have a fatal allergic reaction when given the universe's Truth Serum, which ironically was intended to prevent torture, but obviously, most people who know anything couldn't be given it. Because of the protagonist's odd medical history, he wasn't doctored in this way, but instead has an odd allergic reaction to fastpenta (becoming a Talkative Loon), and is able to exploit this to beat one interrogation he's subjected to in the series. His clone brother Mark, who has an undamaged metabolism, has been doctored to have an allergy to fastpenta and would die if he received it.
 * This usually isn't a suicide mechanism though. It is standard policy for profesionals to first test for a fastpenta enduced allergy before using the drug. Thus it's unlikely that anyone important enough to have an enduced allergy will be subjected to fastpenta without testing for it (don't want to accidentally kill a captive before you get information out of him). In practice this usually means the important operatives get to enjoy the old fashioned interrogation methods.
 * Thursday Next: In The Eyre Affair, when an associate of Acheron Hades started to tell the authorities what he knew, he spontaneously combusted.
 * Labyrinths of Echo had this happened a few times over the main series and prequels. The "non-disclosure" enchantments and oaths are fairly common in the World of Rod. Some kill the subject trying to reveal the secret, others simply prevent talking. Even with the safest enchantments, the problem is that when they directly clash against magic used to get the prohibited answer (or even non-specific mind control effects used to force revealing the secret), results tend to be weird and very messy.

Live-Action TV

 * The Priors in Stargate SG-1 are genetically programmed to burst into flame if they ever lose faith in their gods, The Ori. Though, Priors are so fanatically devout that this is hardly ever an issue.
 * The brainwashed za'tarc assassins are programmed to commit suicide if their mission fails or if someone tries to mess with their brainwashing.

Tabletop Games

 * Black Hats in the Deadlands RPG have microchips implanted in their skulls that explode if they reveal secrets.

Video Games

 * This is the fate of In Barkley, Shut Up and Jam: Gaiden.

Western Animation

 * Superman: Lex Luthor remotely shuts down Metallo after he is captured in in Justice League Unlimited, but it isn't made clear whether this kills him or simply leaves him out of commission until someone can figure out how to fix him.
 * In Totally Spies!, one Big Bad turned out to be an android who was only following the programming of the scientist who created him, who was also evil. He seemed to be the scientist until the very end, when he had a Robotic Reveal and explained everything, including that he was programmed to self-destruct if he ever revealed he wasn't human. Which he promptly did.