|Fig. 1: The grave of Alexander Litvinenko in Highgate Cemetery in London. Source: Wikimedia Commons.|
Raised by his grandfather in the small Russian town of Nalchik, Alexander Litvinenko was drawn early to military service. Following in his father's and grandfather's footsteps, he joined the military immediately after high school. He quickly climbed the ranks to lieutenant and by age 26 was asked to join the KGB to work in counter-intelligence.  He later collaborated with the Moscow police to investigate the massive organized crime syndicate in the Russian capital.
When the KGB transformed into the FSB (Federal Security Service), Litvinenko was promoted to direct investigations regarding internal corruption. In addition to his position with the FSB, Litvinenko served as part-time security detail for Boris Berezovsky, a wealthy Russian businessman and mathematician. However, in late 1997 Litvinenko received an FSB order to assassinate Berezovsky, his friend and employer. He did not carry out the killing but instead went directly to Vladmir Putin, then head of the FSB and future Russian president.  To Putin, he enumerated the extensive corruption within FSB, but Putin was unimpressed. Putin did not want to meet anyone who could corroborate Litvinenko's accusations and had no interest in exposing FSB corruption.
Frustrated with Putin's inaction, Litvinenko took matters into his own hands. Breaking with the FSB chain of command, he held a press conference along with four masked men denouncing corruption at the FSB and revealing assassination orders.  In the midst of a financial crisis, the country did react as Litvinenko had hoped. Following the press conference, Putin dismissed Litvinenko from the FSB, criticizing a lack of evidence. Litvinenko was arrested and held in notorious Moscow prisons, but the charges against him were eventually dropped. 
Upon release from prison, Litvinenko and his family fled Russia and claimed asylum in the UK. Rather than remain quiet in his new home, Litvinenko remained outspoken about corruption in the Russian government. He claimed the FSB staged a hostage crisis and implicated Putin in the assassination of renowned journalist Anna Politkovskaya among many other accusations. [4,5]
On November 1, 2006, Litvinenko fell ill and was hospitalized with apparent food poisoning. However, his symptoms remained severe long after acute food poisoning should have subsided. As his condition worsened and his hair fell out, doctors suspected thallium poisoning.  Initial tests confirmed their hypothesis. They began treatment with "Prussian Blue," an antidote dye for thallium poisoning. Yet Litvinenko's symptoms did not perfectly align with thallium poisoning. Thallium deteriorates muscle tissue while leaving bone marrow intact. Litvinenko maintained muscle strength, but the poison was destroying his bone marrow.  He did not respond to the Prussian Blue treatment. On November 23, Litvinenko went into cardiac arrest and died soon after.
Hours after Litvinenko's death, a British nuclear lab identified the lethal poison: the radioisotope polonium-210, an alpha emitter. When presented with potential radiation sickness, doctors are trained to test for gamma radiation since it can penetrate human skin. Alpha radiation is rarely a concern because alpha particles cannot even penetrate a sheet of paper. However, if an alpha-emitting substance is ingested it is extremely deleterious to internal organs. Once within the body low energy alpha radiation shreds DNA, killing cells. The alpha radiation especially targets rapidly dividing cells present in bone marrow and hair follicles, explaining Litvinenko's symptoms. Given polonium-210's half-life of 138 days, Litvinenko ingested roughly 10 micrograms of polonium which is approximately 200 times the lethal dose of the radioisotope.
|Fig. 2: The radioisotope polonium-210 was used to poison former FSB agent Alexander Litvinenko. Source: Wikimedia Commons.|
On his deathbed Litvinenko dictated a final statement to his friend microbiologist and activist Alex Goldfarb. In his dying words, Litvinenko openly accused Putin of orchestrating the poisoning. Putin denied any involvement, but the polonium trail at least suggests the killer had ties to Russia. Russia produces nearly all of the world's legal polonium-210 supply, and the amount of polonium used to kill Litvinenko could only be produced in a large nuclear reactor.  Based on Litvinenko's own account and the polonium trail, the most likely culprit is Andrei Lugovoy, the former head of security for one of Berezovsky's companies. British authorities conducted a full investigation into Litvinenko's murder and concluded Lugovoy to be the primary suspect. They requested his extradition from Russia, but the Russian government refused, citing a lack of evidence. They proposed conducting their own trial on Russian soil, but as of 2011 no suspects have been charged in the death of Alexander Litvinenko.
 "Alexander Litvinenko," The Telegraph, 25 Nov 06.
 A. Goldfarb and M. Litvinenko, Death of a Dissident: the Poisoning of Alexander Litvinenko and the Return of the KGB (The Free Press, 2007).
 J. Evans, "How Russians Such as Alexander Litvinenko Took on Their Government," London Times, 10 Nov 09.
 D. Satter, "The Truth About Beslan," The Weekly Standard, 13 Nov 06.
 "Obituary: Alexander Litvinenko," BBC News, 24 Nov 06.
 M. Townsend, "Poisoning of Russian Agent Raises Fears of UK Vendetta," The Guardian, 19 Nov 06.