(Reuters) - Boston Marathon bomber Dzhokhar Tsarnaev, who has been sentenced to death, filed a motion in federal court on Monday seeking a new trial, according to court records.
The preliminary motion for a new trial cited a lack of evidence in his trial this spring, according to documents filed in federal court in Massachusetts.
Tsarnaev was convicted in April of killing three people and injuring 264 in the bombing near the finish line of the world-renowned Boston Marathon in 2013, as well as fatally shooting a police officer three days later.
The same jury voted for execution by injection in May.
At his formal sentencing on June 24, the 21-year-old ethnic Chechen apologised and admitted he and his now-dead older brother carried out the attack.
Attorneys for the convicted bomber described the motion as a "placeholder" and said they would spell out reasons for seeking a new trial in additional filings by Aug. 17.
Legal manoeuvring over Tsarnaev's fate could play out for years. Just three of the 74 people sentenced to death in the United States for federal crimes since 1998 have been executed.
Three people died in the bombing: Martin Richard, 8, Chinese exchange student Lingzi Lu, 26, and restaurant manager Krystle Campbell, 29.
Three days later, Tsarnaev and his 26-year-old brother, Tamerlan, shot dead Massachusetts Institute of Technology police officer Sean Collier, 26.
Tamerlan Tsarnaev died following a gunfight with police that ended when Dzhokhar ran him over with a car.
At trial, prosecutors described the brothers as adherents of al Qaeda's militant Islamist ideology who wanted to "punish America" with the attack on the marathon.
Tsarnaev's attorneys admitted their client had played a role in the attack but tried to portray him as the junior partner in a scheme hatched and driven by his older brother, who was killed in a shootout with police a few days after the bombing.
Reporting by Suzannah Gonzales and Ellen Wulfhorst; Editing by Barbara Goldberg and Bill Trott