He and his daughter Yulia were found slumped on a public bench in Salisbury, and the British authorities said they were sickened by a Soviet-made nerve agent.
The second of two Russians who Britain blames for the poisoning of former Russian spy Sergei Skripal was named by investigative website Bellingcat on Monday as a military doctor for Russia's GRU intelligence service.
The suspect identified as Petrov was actually Dr Alexander Yevgenyevich Mishkin, the Bellingcat group said.
The website said it would publish the report on Tuesday.
Bellingcat said that sources who knew Mishkin's family said they believed he had been given the award for actions in Crimea, or for being part of a special forces unit that helped Ukraine's pro-Russian leader Viktor Yanukovych flee the country after he was toppled from power.
British prosecutors charged Petrov and another man they named as Ruslan Boshirov in absentia with attempted murder for the Novichok nerve agent attack on Skripal and his daughter in the English city of Salisbury in March, but said they believed the suspects had used aliases to enter Britain.
He was recruited by the secretive GRU, given the undercover identity of Alexander Petrov when he was stationed in Moscow and made multiple trips to Ukraine, the investigative group said.
The reported naming of the second Novichok suspect is the latest embarrassment for Putin's intelligence services after a bungled cyber attack was exposed by Dutch investigators last week.
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"Until early September 2014, Mishkin's registered home address in Moscow was Khoroshevskoe Shosse 76B - the address of the headquarters of the GRU", Bellingcat's investigation concluded.
The 39-year-old graduated from one of Russia's elite Military Medical Academies, the group's website said.
Unlike the case of Anatoliy Chepiga, "Petrov"'s cover identity retained most of the biographical characteristics of the authentic Mishkin - such as the exact birth date, first and patronymic name, and first names of his parents.
He refused to comment on the Bellingcat findings specifically, as did a spokesman for the Home Office.
Police officers stand outside the house of former Russian double agent Sergei Skripal in Salisbury, England, March 6, 2018.
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.
"We shouldn't also forget that there was a big effort made by our police and MI5 to spot them in the first place, track their movements and also the huge effort that went in to develop the intelligence that helped guide us to the door of the GRU itself".
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. Last week the U.S. Department of Justice indicted seven named GRU officers on charges they had hacked global organizations, including the Organization for the Prohibition of Chemical Weapons (OPCW).