Federal prosecutors have urged a judge to reject a request by lawyers for Boston Marathon bomber Dzhokhar Tsarnaev (joh-HAHR' tsahr-NEYE'-ehv) to strike one of the aggravating factors used to argue he deserves the death penalty.

On Monday, Tsarnaev's lawyers said prosecutors haven't presented evidence of the impact the death of the youngest marathon victim had on his family.

On Tuesday, prosecutors responded that they have shown that 8-year-old Martin Richard "was a beloved son and brother" whose slaying was witnessed by his family and caused "grievous harm and continuing grief."

Tsarnaev was convicted of 30 counts in the 2013 bombing. Closing arguments in the sentencing phase are scheduled for Wednesday. The same jury will decide whether he is executed or spends the rest of his life in prison.