BOSTON — In his first public appearance since he was captured hiding in a boat in a Boston suburb almost three months ago, Dzhokhar Tsarnaev, the surviving suspect in the Boston Marathon bombings, pleaded not guilty on Wednesday to 30 federal charges contained in a sweeping terrorism indictment.

With his left forearm in a cast or heavy bandage and with about three dozen victims and their family members looking on, Mr. Tsarnaev stood before a United States magistrate judge, Marianne B. Bowler, and said “not guilty” seven times as he was asked to enter a plea to different criminal counts covering his alleged role in killing three people and wounding more than 260 near the finish line of the race on April 15.

Most of the charges could mean the death penalty or life imprisonment if he is convicted. Mr. Tsarnaev has also been charged in the shooting death of a Massachusetts Institute of Technology police officer three nights after the bombings.

Mr. Tsarnaev, 19, wore an orange jumpsuit over a dark T-shirt and fidgeted as he stood to make his pleas, speaking with an accent, during a hearing that lasted only about eight minutes. When he entered the courtroom, two women believed to be his sisters gasped and began to cry. Several other supporters in the courtroom whispered “yes” the first time he entered a plea of not guilty. One side of his face appeared injured or almost frozen. He smiled at the two women and made a kissing motion toward them when he left.