FBI wiretap recorded suspect in 2017 Halloween truck attack for 3 years prior

The day before he allegedly took a rented truck for a deadly drive down New York City's West Side Highway bike path, Sayfullo Saipov was secretly recorded on an FBI wiretap, according to newly filed court documents.

The contents of the recorded conversations were not revealed so it is impossible to know whether Saipov was overheard discussing the Halloween 2017 attack, but defense attorneys said that "one of the recordings was from October 30, 2017."

Other conversations were recorded over a three-year period, according to the court filings, suggesting Saipov may have been talking to other people of interest to the FBI.

Defense attorneys disclosed the existence of the intercepted communications as part of a motion to suppress statements Saipov made to the FBI during his interrogation.

That Saipov was under surveillance on the eve of the attack and was still able to carry it out showed the challenge of stopping a so-called lone wolf like him.

"What it says is that the criteria the FBI has been forced to use to assess risk has been flawed for years," said John Cohen, former acting undersecretary at the Department of Homeland Security who is now an ABC News contributor. "To be considered a high-risk threat from a terrorism perspective there has to be coordination or collaboration with a known terrorist group. Absent that the FBI is somewhat hamstrung in what they can do."

Saipov, whose alleged attack killed eight people, is scheduled to stand trial next year. Federal prosecutors are seeking the death penalty.