Lawyers for a man charged with killing eight people in a terrorist attack on a New York City bike path said in a court filing Friday that they had learned the FBI had intercepted his communications, though it was unclear when that surveillance began.

"We are still waiting for more information from the government about the nature and basis of the wiretaps," lawyers for Sayfullo Saipov wrote as they challenged case evidence, including statements he made to investigators and the government's plan to seek the death penalty.

Saipov is accused of driving a truck down a Manhattan bike path on Halloween in 2017, running over cyclists, before crashing his vehicle into a school bus. He was shot by a police officer and arrested at the scene.

In a portion of their court filing attacking evidence in the case, Saipov's lawyers said it was clear that two FBI agents who questioned Saipov at a hospital the day after his arrest interrogated him "about matters and contacts that overlap with surreptitious FBI surveillance of Mr. Saipov's communications."

A portion of the court filing dealing with that surveillance was blacked out in the public version of the document and it was unclear when the surreptitious surveillance occurred.

The lawyers asked the court to throw out statements Saipov made to the agents, saying he was questioned while under the effect of powerful drugs as he recovered from gunshot wounds.

A spokesman for prosecutors declined comment.

Saipov goes to trial next fall. His lawyers noted that New York is a non-death-penalty state. They say federal death penalty law is too flawed to enforce.

The lawyers already have opposed the death penalty in the case on other grounds, including tweets that were sent about the attack by President Donald Trump.

After Saipov's arrest in the deadliest attack on New York City since Sept. 11, 2001, Trump tweeted, "SHOULD GET DEATH PENALTY" and "Should move fast. DEATH PENALTY."

The lawyers are also asking the judge to exclude information seized from cellphones found when Saipov was arrested.

Saipov, 30, moved to the United States legally in 2010 from Uzbekistan. He lived in Ohio and Florida and worked as a commercial truck driver before living more recently with his family in Paterson, New Jersey.

Court papers say that after his arrest, he told authorities that he was inspired by ISIS video and that he had used a truck in the attack to inflict maximum damage against civilians. He's pleaded not guilty.