Todashev and Tsarnaev
Ibragim Todashev (l) and Tamerlan Tsarnaev WFTV/Reuters

A defence attorney for Dzhokhar Tsarnaev, 19, who faces the death penalty if convicted of carrying out the bombings at the Boston Marathon in 2013, claims the FBI attempted to recruit his older brother Tamerlan to spy on Muslims and the Chechen community in the city.

The FBI made more than one visit to talk with (Tamerlan's parents) and Tamerlan
Dzhokhar Tsarnaev's defence attorney

Tamerlan Tsarnaev, 26, who was shot dead after allegedly carrying out the attacks, in which three people died, has also been linked to a gruesome triple murder in the city which took place on 11 September, 2011 – ten years to the day after the deadly terror attacks on New York and Washington.

The bodies of apartment owner Brendan Mess, 25, Erik Weissman, 31, and Raphael Teken, 37, were found in a Waltham, Boston apartment on 12 September 2011, their throats slashed, bodies placed face down and covered with marijuana and thousands of dollars in cash.

Boston bombing Martin Richard
Dzhokhar Tsarnaev apparently walking past eight-year-old Martin Richard, youngest victim of the bombing

Tamerlan Tsarnaev was a close friend of Mess, visiting the Waltham apartment regularly. The two men also worked out at the Wai Kru mixed martial arts gym. Despite his name being mentioned by several friends during interviews he was never questioned – and never attended the funeral or memorial service.

Following Tsarnaev's death, an FBI agent went to interview his friend Ibragim Todashev in Florida. Todashev also knew Mess and trained at the same gym. When asked about the killings in Waltham he apparently implicated Tsarnaev but then tried to attack the agent with a metal pole and was shot dead. The FBI agent responsible has been cleared of any wrong-doing.

Now journalists in the US are asking how much information the FBI had about Tsarnaev and his murky past and whether the FBI might even have prevented the bombings taking place had they followed up leads about Tsarnaev earlier.

Dzhokhar's defence attorney filed a court motion on Friday which said: "We base this on information from our client's family and other sources that the FBI made more than one visit to talk with (Tamerlan's parents) and Tamerlan, questioned Tamerlan about his internet searches, and asked him to be an informant."

However in a statement the FBI rejected the claims, saying there was "no evidence that Tamerlan Tsarnaev was solicited by the government to be an informant."