Prosecutors are likely to focus on their contention that the brothers were partners in the plan to bomb innocent people to get back at the U.S. for wars in Muslim countries. The jury must reach a verdict on 30 federal charges, including use of a weapon of mass destruction resulting in death, bombing of a place of public use resulting in death and the killing of a Massachusetts Institute of Technology police officer several days after the bombings. If Tsarnaev is convicted, which is widely expected given that his lawyers admitted he participated in the bombings, the same jury will hear additional evidence in the second phase of the trial to determine Tsarnaev's punishment. In their notice of intent to seek the death penalty, prosecutors cited a number of aggravating factors outlined in the federal death penalty law, including their allegation that he committed the offense in an especially heinous, cruel and depraved manner; committed the crime after substantial planning and premeditation; and that he is responsible for the death of 8-year-old Martin Richard, a victim who was particularly vulnerable because of his youth. Other aggravating factors cited by prosecutors include their claim that he has shown a lack of remorse and that he targeted the Boston Marathon because it draws large crowds, making it particularly susceptible to an act of terrorism. Some mitigating factors listed in the federal death penalty act include the defendant being under "unusual and substantial duress;" the defendant's participation in the offense being relatively minor; and the defendant committing the offense under "severe mental or emotional disturbance." Even though Tsarnaev faces federal charges in the killing of MIT police Officer Sean Collier and in a violent confrontation with police in Watertown days after the bombings, he also faces state charges for those crimes.