Cyanide, deadly nightshade and pesticides have disturbingly similar symptoms to the toxin that took a powerful character's life, writes Rachel Nuwer. Warning: this post is laced with potent spoilers.

Game of Thrones fans have little love for young King Joffrey Baratheon. The voracious-for-power, know-it-all teen wears his expression in a permanent sneer. He executes innocents on a whim, tortures women, regularly insults his mother and elders and has no regard for anything but his own Narcissistic self-interest. All told, this character is a sadistic little shit. Which is why, when a deadly poison permanently wiped the smirk off Joffrey's face in season four of GoT, fans rejoiced.

For all his faults, however, no one can argue that Joffrey's death was anything less than deeply horrific. That nightmare scenario was so realistically portrayed that it creates an unsettling suspicion that the poison was not purely the stuff of fiction. Dragons aside, author George R.R. Martin does have a tendency to borrow from non-fiction when devising some of his most gruesome plot twists (the Red Wedding, for example, was loosely based on historic events, and in the past, some people were indeed executed by molten gold). Moreover, in historic times, poisonings were a common means of murder—including of those in positions of power.

This all poses the question: was the potion that killed Joffrey based on a real-life poison?

Answering this question first requires analyzing the symptoms produced by the mystery formula.

When Martin concocted the strangler—the name of the poison that claimed Joffrey's life—he imagined a tasteless, plant-derived toxin that causes death by asphyxiation. As viewers witnessed in "The Lion and the Rose," the victims do not go gently.

Moments after consuming a suspect sip of wine and having a bite of pie1, Joffrey complains of dryness in his mouth.

He clears his throat, and then begins to cough, at first lightly but then violently, as if choking.

He vomits as his body tries to rid itself of the toxin. Unable to breathe, he writhes in panicked spasms and his skin turns bluish.

He begins to hemorrhage: blood pools in the whites of his eyes and streams from his nose, while red spotting appears in his cheeks.

Death occurs within minutes.

Identifying the killer

While no real-world poison produces exactly the same results, there are some promising candidates that—with either a little chemical or cinematic doctoring up—could easily act as strangler stand-ins. Both Marsha Ford, director of the Carolinas Poison Center, and Deborah Blum, a professor of journalism at the University of Wisconsin and author of The Poisoner's Handbook, think that cyanide is the closest match. A tiny amount of cyanide can produce toxic results, and that poison is quickly absorbed from the gut. It causes burning in the throat, Ford explains, and can also lead to pulmonary edema (a fluid build-up in the lungs), both of which could trigger the coughing fit. "Cyanide is famous for causing people to start coughing when they swallow it," Blum says. She cites a case from 2012 when a man found guilty of arson committed suicide in the courtroom by ingesting cyanide. He began violently coughing and choking, and then died minutes later. "It causes fast-moving chemical suffocation," Blum says.

Vomiting and confusion are also in line with cyanide's effects, as is the blueness in the skin, caused by lack of oxygen reaching his cells. Among other fatal biochemical tamperings, cyanide inhibits an enzyme called cytochrome oxidase, which plays a key role in oxidative phosphorylation—the body's system for generating energy through production of ATP. When that system is halted—gasp as he might—a person's cells can no longer access life-giving oxygen, and the body begins to die. As death nears, the person's skin can turn blue—a clinical effect called cyanosis. "They begin to have air hunger," Ford says. "The cyanosis I saw in the episode is typical of someone who's just not getting oxygen into their cells."

Just as the stangler comes from the leaves of a plant, cyanide is distilled from natural products, including peaches, cherries and apricots. About 0.2 grams of potassium cyanide slipped into a person's drink would be enough to kill him. The red wine's strong taste—and the fact that the drinker was likely somewhat inebriated already—would have thrown him off to the slightly "bitter almond" flavor that toxin carries, Ford says. Cyanide's natural roots, low required dose and lack of flavor in this situation all line up with the strangler.

On the other hand, some of Joffrey's symptoms do not match perfectly with cyanide. The dramatic bleeding is not typical, especially from the eye ("A bit excessive," Ford says). While sodium cyanide is a more caustic poison than potassium cyanide and can sometimes result in a telltale bloody froth around the mouth, Blum points out that this usually doesn't cause streaming. To cause the hemorrhaging, it could be possible to either concentrate cyanide to make it more lethal, or combine it with another poison. A 15th century Italian family called the Borgia did just that, experimenting with combinations of arsenic and cyanide to use on their enemies. "These are already efficient poisons, but the people using them for assassination purposes wanted them to be no fail," she says. "You could imagine that something like the strangler came from a cyanide-like poison that someone had figured out a way to concentrate and ramp up."

A less glamorous explanation, however, is that the bleeding was simply a result of the violent coughing Joffrey experienced in his death throes, Ford says. This would also explain the red splotches— popped blood vessels called petechia—that appeared on his cheeks. An underlying blood-related condition such as Von Willebrand's disease would also make a victim more prone to hemorrhaging, Ford adds.

Cyanide is not the only candidate, however. Deadly nightshade—a favorite poison in medieval times—is another potential strangler. Rumor has it that Emperor Augustus used it to murder foes in ancient Rome, so this plant is no stranger to high-profile plots. The leaves, stems and berries of deadly nightshade contain tropane alkaloids—extremely potent toxins that disrupt nervous system functioning. As neurotransmitters are blocked, the victim will begin to stagger, convulse, lose his vision and experience an extremely dry mouth and throat, creating a sensation of choking. Blood vessels also dilate, causing the victim to become very hot and to turn red. "I noticed that in the character's face," says John Trestrail III, director of the Center for the Study of Criminal Poisonings. Like cyanide, however, hemorrhaging, is not a normal symptom of deadly nightshade, and neither is the speed by which Joffrey succumbed to his fatal dose.

Modern spin

Cyanide and deadly nightshade are old time poisons and seem well suited for GoT alchemists who would be working in a setting more akin to that of medieval European than of today's high-tech labs. But if the GoT poisoners did have access to current technologies, some modern strangler equivalents do come to mind, Ford says. These include sodium azide, found in some car airbag systems, and fluoroacetate, a pesticide sometimes used on coyotes in the US and invasive mammals in New Zealand. Both of those concoctions produce cyanide-like symptoms if consumed, although they don't act as quickly.

A pesticide called aluminum phosphide is another modern-day candidate. It's even more lethal than cyanide, Blum says, and produces similarly nasty symptoms. These include complete oxygen deprivation in the extremities, vomiting and trauma within the body—which can cause bleeding.

Unfortunately, the murderous potions don't stop there. According to Trestrail, with the aid of technology and chemical knowledge, chemists today could likely create an even more accurate doppelganger of the purple wedding poison. It might not perfectly mimic each and every symptom Joffrey experienced, but they could probably get pretty close. "People are always experimenting," he says. While this often results in better living through chemistry, Trestrail points out that there's a flipside to that, too: "Better dying through chemistry."

Modern monster or old horror, what is true for all of these poisons is that, exposed to in high enough doses, getting ahold of an antidote (if one even exists) in time to save the victim's life would be highly unlikely. "For the poisons that are super fast acting, you'll have a jolt of awareness, but not in time to save yourself," Blum says.

Which is exactly what happened to Joffrey. Lying on the ground, suffocating, he desperately looks up at his mother for help. But there is nothing she can do. Finally, he, too, seems to understand that all is lost. No longer the haughty Lord of the Seven Kingdoms, Joffrey dies as a helpless, terrified boy.

1. Other proposed delivery vehicles include the gems or clothes Joffrey wore.