The court was shown a never-before seen photograph of Tsarnaev, dressed in an orange prison jumpsuit flipping his middle finger at a surveillance camera in a cell before his first arraignment.
"This is Dzhokhar Tsarnaev, unconcerned, unrepentant and unchanged," said assistant US attorney Nadine Pellegrini in her opening statement at the penalty stage of his trial.
The former student was convicted earlier this month on all 30 counts related to the April 15, 2013 bombings, the murder of a police officer, a carjacking and a shoot out.
"The death penalty is appropriate because Dzhokhar Tsarnaev planned and plotted to kill," Pellegrini told jurors.
"His character makes the death penalty appropriate."
She also displayed large color photographs of the victims, looking happy and well, before they were killed.
The "unbearable, indescribable, inexcusable, senseless" attacks, she said, proved Tsarnaev and his twisted, extremist ideology were "destined to become America's worst nightmare."
"He shared his beliefs in terrorism with his brother," 26-year-old Tamerlan who was killed by police while on the run, and "the people in the crowd were his enemies," she said.
The federal court room was packed for the first day of the penalty phase, which began with instructions from the judge to the jury, the same 12-member panel that convicted Tsarnaev on April 8.
