Lawyers for a college friend of Boston Marathon bomber Dzhokhar Tsarnaev (joh-HAHR' tsahr-NEYE'-ehv) are trying to prevent the family of a slain Massachusetts Institute of Technology police officer from testifying at his sentencing.

Dias Kadyrbayev (DY'-us kah-dur-BY'-ehv) is to be sentenced Tuesday after pleading guilty to impeding the investigation of the 2013 bombing, which killed three people and injured more than 260.

His attorneys filed a motion Friday in federal court in Boston seeking to prevent victim impact statements by relatives of MIT Officer Sean Collier, who was shot in an encounter with Tsarnaev and his brother. The Boston Herald (http://bit.ly/1RwvUOu ) was first to report on the motion.

Collier's family said in a statement released this week that Kadyrbayev might have prevented Collier's death by helping authorities find Tsarnaev.