Under tight security surrounding the Boston courthouse, the Dzhokhar Tsarnaev marathon bombing trial got underway today with opening statements.

Tsarnaev's defense attorney put forth an argument that admits client guilt but that he had fallen under the influence of his older brother and therefore he should not receive the death penalty.

Prosecutors used their opening statement to say Tsarnaev carried out a cold-blooded attack to kill people and then went to hang out with buddies afterward as if nothing happened.

Tsarnaev, 21, faces 30 charges in connection with the April 15th, 2013 bombing at the Boston Marathon. Three people died in the bombings and more than 260 were injured.

The trial is expected to last several months.