My understanding is that there was no conviction, and therefore may not have been deportable since he was here legally.
If there was a conviction, there should be a public record of that.
Judicial Watch: One of Boston suspects should have been deported
PHOENIX — The slain Boston Marathon bombing suspect should have been deported in 2009, said Chris Farrell with Judicial Watch.
Farrell said 26-year-old Tamerlan Tsarnaev was in the United States after being offered asylum but should have been deported after being convicted of domestic violence.
“The Citizenship and Immigration Services, part of [the Department of Homeland Security], did nothing,” he said. “Makes no connection between his criminal behavior and his status of trying to gain citizenship here.”
http://ktar.com/23/1628322/Judicial-Watch-One-of-Boston-suspects-should-have-been-deported