The poison used, according to British authorities, was novichok, an especially unsafe nerve agent, and, analysts say, it was nearly certainly Mishkin's role to apply the poison, which is thought to have been smeared on the handle of Skripal's front-door.
The UK-based investigative website Bellingcat has said it has identified the second suspect in the Salisbury nerve agent poisonings as a doctor belonging to Russia's military intelligence agency the GRU.
Bellingcat said it gathered its information from open sources and "testimony from people familiar with the person".
Bellingcat said on its website that the man British authorities identified as Alexander Petrov is actually Alexander Mishkin, a doctor working for the Russian military intelligence unit known as GRU.
The website alleges Miskin travelled under the alias Alexander Petrov.
The UK in early September accused two Russian men, Alexander Petrov and Ruslan Boshirov, of attempting to assassinate ex-spy Sergei Skripal with a military-grade nerve agent in Salisbury, England in March 2018.
Bellingcat said he made multiple trips to Ukraine.
The BBC has contacted two people who knew Mr Mishkin as a child in the village of Loyga in the north of Russian Federation, who confirmed from photographs that he is the man seen in images released by police after the Salisbury attack in March.
The father and daughter survived after a lengthy hospital stay in intensive care.
The activities of the GRU have come under further scrutiny after the agency was accused of trying to hack the global chemical weapons watchdog which is investigating the Salisbury nerve agent attack.
He was recruited by the GRU while at one of Russia's military medical academies, eventually becoming a military doctor.
Putin's spokesman, Dmitry Peskov, said the Kremlin wouldn't discuss investigative reports and media articles on the Skripal poisoning.
Using these details and searching through leaked databases of Russian housing and other records, researchers from Bellingcat were able to find a match, first tracing Mishkin to the St. Petersburg military academy where he studied.
They had noticed that other GRU officers retained their first name, birthdate and place of birth when they were given new identities. The researchers said multiple residents in Mishkin's home village, Loyga, had confirmed a photograph of the suspect "Petrov" was in fact Mishkin.
The suspects were identified as GRU agents and Theresa May said their actions were not a "rogue operation" and would have been approved at a senior level in Moscow.
Despite the Bellingcat investigation appearing to have exposed the GRU, British security minister has warned against underestimating the threat of Russian Federation.
The U.S. Justice Department also charged seven GRU officers in an alleged worldwide hacking rampage that targeted more than 250 athletes, a Pennsylvania-based nuclear energy company, a Swiss chemical laboratory and the chemical weapons watchdog.
Russia's foreign minister Sergey Lavrov has dismissed the allegations, saying the men who were expelled from Holland had been there on a "routine" assignment to provide cybersecurity support for Russia's embassy.
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