Shortly after his conviction in 2011 on charges including conspiring to kill American citizens, the Russian arms dealer Viktor Bout relayed a defiant message through his lawyer, even though he faced the prospect of decades in prison.
Mr. Bout, his lawyer said, “believes this is not the end.”
More than a decade later, Mr. Bout, 55, may be nearing a chance for a new beginning, even though he has served less than half of his 25-year prison sentence.
The United States, trying to negotiate the release of two Americans imprisoned in Russia — the basketball star Brittney Griner and a former Marine, Paul Whelan — proposed in June to exchange them for Mr. Bout, according to a person briefed on the negotiations.
Russian officials have pressed for Mr. Bout’s return since his conviction in 2011 by a New York jury on four counts that included conspiring to kill American citizens. Prosecutors said he had agreed to sell antiaircraft weapons to drug enforcement informants who were posing as arms buyers for the Revolutionary Armed Forces of Colombia.
The attorney general at the time, Eric Holder, called Mr. Bout (pronounced “Boot”) “one of the world’s most prolific arms dealers.” Mr. Bout become notorious among American intelligence officials, earning the nickname “Merchant of Death” as he evaded capture for years. His exploits helped inspire a 2005 film, “Lord of War,” that starred Nicolas Cage as a character fashioned after Mr. Bout.
Now, he is probably the highest-profile Russian in U.S. custody and the prisoner Russia has campaigned the most vociferously to have returned. If he is sent back to Russia, it is likely to re-ignite the debate over the wisdom of engaging in prisoner exchanges for Americans the United States considers “wrongfully detained” — as is the case with Ms. Griner and Mr. Whelan.
In interviews with journalists, Mr. Bout has repeatedly denied accusations that he worked for Russian intelligence agencies. But Mark Galeotti, an expert on Russia’s security services, said there were strong signs — Mr. Bout’s education, his social and professional networks, and his logistical skills — that he is a member, or at least was in close collaboration with, Russia’s military intelligence agency, known as the G.R.U.
“That is also the opinion of U.S. and other authorities — and it explains the reasons Russia has been so assiduously campaigning to get him back,” said Mr. Galeotti, a lecturer on Russia and transnational crime at University College London. “All countries try to get their citizens out of rough jurisdictions, but it is clear that it has been a particular priority for the Russians in getting Viktor Bout back.”