Stephen Silva was convicted of giving a firearm to Boston Marathon bomber Dzhokhar Tsarnaev.
Tsarnaev’s legal team said the convicted bomber doesn’t deserve the death sentence.
Other infamous convicts, including the "Shoe Bomber," also are housed at the Colorado prison.
The move was expected from his legal team following his conviction and sentencing earlier this year.
Two dozen victims and survivors addressed Dzhokhar Tsarnaev earlier on Wednesday.
Khairullozhon Matanov was sentenced for obstructing the Boston Marathon bombing investigation.
The jury deliberated for almost 15 hours; defense lawyers were expected to quickly appeal the death sentence.
Assistant U.S. Attorney said the ethnic Chechen had turned against his adopted country.
Here's what we know about the Boston Marathon bomber from the two phases of his trial.
Boston Marathon bomber Dzhokhar Tsarnaev told a Roman Catholic nun and prominent death-penalty opponent that "no one deserves to suffer" as the victims of the deadly 2013 attacks had.
Dzhokhar Tsarnaev apologized after he raised his middle finger to a cell surveillance camera following his arrest in 2013, a witness said.
Once a heavy drinker, a Boston Bomber transformed into someone obsessed with Islam.
The defense argued Dzhokhar Tsarnaev fell under the sway of his older brother.
Boston Bomber Dzhokhar Tsarnaev is being tried at the courthouse.
The debate over the death penalty has become even more contentious as of late.
Matanov will be sentenced on June 18.