Boston Marathon bomber Dzokhar Tsarnaev filed a motion on July 6 demanding a new trial, less than two weeks after he was sentenced to death.
Tsarnaev's defense team filed a preliminary motion for a new trial for his conviction and death sentence.
The lawyers said they will file a detailed appeal by August 17.
Defense attorneys routinely file such motions challenging jury verdicts.
Tsarnaev, 21, was convicted of 30 charges in the 2013 attack, which killed three people and injured more than 260.
The same jury recommended the death penalty, and a federal judge on June 24 sentenced him to death.
Tsarnaev acknowledged that he carried out the bombing with his older brother.
During the trial, his defense lawyers conceded Tsarnaev's role in the bombings, but urged jurors to vote against sentencing him to death.