On Nov. 5, 2012, Alexander Perepilichnyy went for a jog around his gated neighborhood in the posh southwest London suburb of Weybridge. The 44-year-old was handsome and in good physical health. Mentally, however, he was a nervous wreck. Perepilichnyy was a brilliant mathematician who had made a fortune in finance in Moscow, but had fled Russia in 2010 before helping expose a $230 million tax fraud ring allegedly involving senior Kremlin officials.

Other Russian whistleblowers had been imprisoned, even killed. Now Perepilichnyy feared for his own safety. He told friends he had received death threats. He was careful about appearing in public. He even took out a large life insurance policy.

For good reason. As he ended his run, Perepilichnyy suddenly collapsed. By the time paramedics reached his mansion, he was dead.

Friends and business colleagues cried foul, suspecting a professional hit ordered by the powerful figures Perepilichnyy had burnt back in Russia. But local police could find no evidence of wrongdoing and quickly closed the case.

On Monday, however, officials announced that they had found traces of a rare and deadly plant poison in Perepilichnyy's stomach. Police have yet to label the case a murder, but a full inquest into the suspected poisoning will take place in September.

The twist in the 2½-year-old case puts Perepilichnyy's death among a seemingly increasing number of high-profile political poisonings. The past decade has seen a handful of infamous poisoning incidents, from the disfigurement of Ukrainian President Victor Yushchenko in 2004 to the bizarre polonium poisoning of Russian spy Alexander Litvinenko in 2006. In 2011, a Chinese billionaire died after eating a dish of cat-meat stew believed to have been laced with the same kind of plant poison detected in Perepilichnyy.

Apolitical poisonings are also in the news. Also on Monday, a nurse in England was convicted of poisoning 22 people, two of whom died. Victorino Chua, who described himself as "an angel turned into an evil person," injected insulin into patients' saline bags.

Add that to recent exhumations of historical figures suspected of being poisoned — from Simon Bolivar to Pablo Neruda and Yasser Arafat — and poisoning appears to be en vogue.

But a British chemistry expert says that poisoning dates back millennia and that what seems like a current trend could simply be a result of recent advances in testing techniques.

"Poisoning may be enjoying a comeback, or it may be that it's harder to get away with it now," says John Emsley, the author of "The Elements of Murder: A History of Poison."

"Forensic chemistry is now so sophisticated that it's possible to detect poisons at levels that previous generations would not have thought possible," he tells The Washington Post. "If someone dies under anything like suspicious circumstances then forensic chemistry will soon realize and find exactly what it is from analyzing parts of the body or fluids. . . . So more people are being detected who in previous generations might have got away with it."

In fact, history presents plenty of famous poisonings, few of which were ever solved. Perhaps the most famous case is also among the least mysterious. In B.C. 399, ancient Greek philosopher Socrates fatally drank hemlock after being sentenced to die by a jury.

Nero, the supposedly mad Roman emperor, is said to have assumed the throne after his mother poisoned the previous ruler with toxic mushrooms. "Even if he was not the instigator of the emperor's death, he was at least privy to it, as he openly admitted; for he used afterwards to laud mushrooms, the vehicle in which the poison was administered to Claudius, as 'the food of the gods,' " Suetonius wrote.

More than a century later, another Roman emperor, Commodus, was allegedly betrayed by his wife but couldn't keep the poisoned food down and so was finished off by his wrestling partner.

At least five popes are rumored to have been poisoned. Pope Clement II died mysteriously in 1049. Nine hundred years later, his body was exhumed and traces of lead discovered, although it's unclear if the poisoning was intentional. In 1978, Pope John Paul I died after just 33 days in power, spawning conspiracy theories of a poisoning inside the Vatican.

Emsley says people normally poison for either political or financial reasons. Either way, their choice in instrument is logical: "Mainly it's the thought that you might be able to get away with it because the person will die and it will appear to be natural causes," he says.

Emsley says poisoning really took off in the Elizabethan era. Shakespeare included poison in his most famous play, as Hamlet's father died from poison poured into his ear as he slept (something Emsley says is probably not possible). But, in reality, it was the Italians who pioneered poison. "There was this easy access to arsenic, which was a byproduct of copper smelting," Emsley says. "Inside the flues of the smelters you get these beautiful white crystals of what was called arsenic. It's actually arsenic oxide. It was soluble in water and tasteless, so it made a very easy way of disposing with somebody without them realizing that they were taking something dangerously toxic."

The chemist calls the 19th century "the golden age of arsenic poisoning" because it was cheap and prevalent across Europe and the U.S. That's when poison became associated with female killers. "It was so difficult in those days for a woman to obtain a divorce," Emsley says. "But you could obtain arsenic fairly easily. It was sold quite openly to put on fly paper to kill flies or as a weed killer. . . . In the 19th century, most poisonings were women trying to dispose of their husbands."

Beethoven and Mozart are both rumored to have been poisoned, Emsley points out, although the evidence is thin. The late Venezuelan president Hugo Chavez was so certain that his hero, Simon Bolivar, had been poisoned — rather than simply dying of tuberculosis — that he ordered Bolivar disinterred on live television almost 200 years after his death. The tests were inconclusive. Other recent exhumations linked to suspicions of poisoning include Palestinian leader Yasser Arafat and Chilean poet Pablo Neruda, a staunch communist whose driver says he received a mysterious stomach injection shortly before his death.

One poisoning in particular came to define the Cold War era. In 1978, Georgi Markov, a prize-winning Bulgarian author who had angered authorities and fled to London, was standing at a bus station when he felt a prick in the back of his leg. He died three days later, the victim of a tiny poison pellet injected via an umbrella by a Bulgarian secret agent, an investigation found.

That same year, more than 900 people died at the Jonestown settlement in Guyana after drinking cyanide-tainted fruit flavored punch, some unwittingly.

Not even Markov's umbrella assassination compares to poisonings in the past decade, which has seen a remarkable run of high-profile assassination attempts. While running for the Ukrainian presidency in 2004, Viktor Yushchenko became deathly ill. His face was partially paralyzed and covered in hideous lesions that transformed his once Hollywood-esque looks. Critics claimed he had simply drank too much and eaten bad sushi, but testing later revealed he had been poisoned with pure dioxin, a component of Agent Orange.

Even stranger was the 2006 poisoning of Alexander Litvinenko. The Russian spy defector became deathly ill just days after meeting with two KGB agents in London. But as Litvinenko's hair fell out and he wasted away inside a hospital, he blamed his illness on Vladimir Putin. "You may succeed in silencing me, but that silence comes at a price," he wrote from his deathbed. "The howl of protest from around the world will reverberate, Mr. Putin, in your ears for the rest of your life."

An investigation later determined that the KGB agents had injected a powerfully radioactive liquid called polonium 210 into Litvinenko's drink. The poison was ingenious, Emsley says. It gave off killer alpha particles but not gamma rays that could set off detectors inside an airport. Litvinenko died, but authorities were able to trace his killer's movements through London by following the alpha particles like a "path of breadcrumbs left by Hansel and Gretel."

Litvinenko was the first victim whose death was conclusively linked to polonium. Like arsenic centuries ago, however, it's likely that many more were killed this way. "You wonder with this Litvinenko case, how many other people might the Russian secret police disposed of using this particular [chemical] agent," Emsley says. "Of course they won't be able to use it now because any suspicious death people will check for polonium."

Which means that assassins have turned to newer, even harder to detect substances such as the one believed to be responsible for the death of Alexander Perepilichnyy. According to British media, authorities discovered a rare plant toxin called gelsemium in the dead man's stomach. The most potent type of gelsemium only grows in Asia, where it is called "heartbreak grass," according to the Guardian.

Emsley says he isn't familiar with the poison and that, so far at least, the evidence looks light. But a 2011 case in China seems to demonstrate the poison's deadly effects. Chinese billionaire Long Liyuan died after eating a bowl of cat-meat stew laced with gelsemium. A local official was arrested for the alleged murder.

But the discovery of gelsemium in Perepilichnyy's system shows that, once again, science has caught up with killers, Emsley says. Authorities have also made it much harder to obtain toxic substances. Even people who try to make their own ricin out of castor oil beans are usually caught.

"If it's a suspicious death, modern chemistry can detect anything even down to the levels of microgram quantities as we've seen from the polonium case of Litvinenko," Emsley says. "There is no such thing as the perfect poison."