NEW YORK -- Preliminary jury selection is underway in the death penalty trial over the 2017 Halloween terror attack on the West Side of Manhattan. 

Lawyers for defendant Sayfullo Saipov claim evidence that others influenced his actions was not turned over in a timely fashion, CBS2's Tony Aiello reported Friday. 

Six foreign tourists and two New Yorkers were killed in the attack on Oct. 31, 2017.

Saipov, radicalized to support ISIS, admits renting a truck and driving it down the West Side bike and pedestrian path. 

Almost five years later, and on the eve of the trial, the defense says vital information was not turned over quickly, as required.

"The defense is alleging that it's been held onto for years, and that they're just dropping it on the defense weeks before trial," said Jason Goldman, a former prosecutor who reviewed the Saipov defense submission for CBS2. 

Saipov's team says it just received evidence "that has been in the FBI's possession for years," claiming "the significance [of this] is extraordinary" in that it bolsters their theory "that [Saipov] was influenced by others who share culpability, yet they are not being prosecuted." 

Evidence of influence by others could help the defense convince jurors to reject the death penalty.

"Although these other actors may not have been criminally prosecuted, although there might not be evidence to hold them accountable for the actual crime, this is mitigation as it relates to the defendant on trial and how he was influenced, perhaps, to commit certain crimes. It builds context around why the crime may have been committed or what could have led to it. And the defense will always look for any and all information which might paint that picture more favorably for their client," said Goldman. 

The defense asked the judge to review how the FBI evidence was handled and why it was handed over so late. The U.S. Attorney's office said it will respond next week. 

Meanwhile, 800 New Yorkers are getting questionnaires as jury selection begins. Prospective jurors are being warned the trial and penalty phase could last from late October into late January. 

Saipov has indicated he's willing to plead guilty and accept life in prison if the U.S. drops its pursuit of the death penalty.