British authorities charged Boshirov and Petrov with the March poisoning of Skripal and his daughter in which they were attacked with the nerve agent novichok, which officials say was spread on a door knob to their home in Salisbury. Amy Kellogg has the story.
"Based on the body of intelligence, the government has concluded that the two individuals named by the police and the Crown Prosecution Service are officers from the Russian military intelligence service, also known as the GRU", British Prime Minister Theresa May told parliament at the time.
Mishkin had travelled to the United Kingdom under the assumed name Alexander Petrov with another Russian agent Anatoliy Chepiga, who came on the false identity of Ruslan Boshirov.
The poison used, according to British authorities, was novichok, an especially risky 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.
Last month, Bellingcat, along with its partner investigators at the news-site Insider, identified the other suspected poisoner as special-forces veteran Anatoliy Chepiga, a colonel in the GRU. The British government has blamed Russian Federation for the attack.
Bellingcat said it identified Mishkin using passport information, phone records, vehicle registration records, other databases and interviews with people who knew him.
The second suspect in the attempted poisoning of a former Russian secret agent has been identified by an investigative website.
Bellingcat also said it had obtained a copy of Mishkin's passport and that a facial recognition analysis of the passport photograph showed it matched a photo of 'Petrov.' Russian officials have dismissed Bellingcat's previous reports, but have refused to engage with their substance.
The father and daughter survived after a lengthy hospital stay in intensive care.
It revealed that Mishkin was born in 1979 in the small village of Loyga, north of Moscow.
The unmasking of a second Russian intelligence officer suspected of carrying out a nerve-agent attack in England earlier this year is prompting behind-the-scenes fury in the Kremlin, which is likely to respond by purging the senior ranks of Russia's military intelligence service, the GRU, Russian media is reporting.
Using this identity, Alexander Petrov, travelled extensively to several European countries including Ukraine and Moldova.
Bellingcat said they had cracked the puzzle of the man's identity partly through a mistake by the GRU, which did not change the first name or birthdate of the agents when it gave them fake identities.
One of the Bellingcat team who ID'd the two GRU agents points out that the inclusion of a doctor on a 2-man team makes it harder to claim these guys were doing something other than handling a deadly nerve agent.
Until September 2014 his registered home address in Moscow was the same as the headquarters of the GRU. Last week the U.S. Department of Justice indicted seven named GRU officers on charges they had hacked worldwide organizations, including the Organization for the Prohibition of Chemical Weapons (OPCW).