Lawyers representing the 62-year-old man accused in an allegedly premeditated rush-hour transit attack that left nearly two dozen injured, 10 of them by gunshots, in Brooklyn on April 12 say the FBI unconstitutionally questioned and searched their client, Frank James, in his cell earlier this week, court papers obtained Thursday show.

James, whose alleged smoke grenade, shooting attack on the N train in Sunset Park triggered the worst commute disruption the city has seen in 20 years,

In a letter sent to U.S. Magistrate Judge Roanne L. Mann of the Eastern District of New York and dated Thursday, attorneys Mia Eisner-Grynberg and Deirdre D. von Dornum claim FBI agents went to James' cell at the Metropolitan Detention Center in Brooklyn on Tuesday, questioned him, took DNA swabs and told him to sign certain documents.

It was 12 days after he had been appointed legal counsel, the attorneys say, and they received no advance notice of the FBI's intentions.

"Contrary to standard practice, the government committed this intrusion absent advance notice to counsel, depriving us of an opportunity to be heard or to be present." Neither did the government provide subsequent notice to counsel," the lawyers said.

Furthermore, the search warrant approving DNA swabs to be taken from James wasn't provided to him, the lawyers said. They claim they only got a copy of the warrant when they asked -- after James had told them what happened and the search was completed, the letter to the judge says.

"It is the standard practice in this District that when the government obtains a search
warrant for buccal swabs from a represented, post-arraignment defendant, the government informs counsel of same before its execution, and offers an opportunity to be present," the lawyers wrote. "This serves as a safeguard to protect the rights of represented defendants. Here, because the government failed to provide notice to counsel before questioning and searching Mr. James, their practice risked violations of Mr. James’s core constitutional rights under the Fourth, Fifth and Sixth Amendments."

The attorneys asked for a court order to compel the government to give them the underlying affidavit upon which the warrant was issued so they can file to suppress any evidence of any kind that was collected during that meeting earlier this week.

An email request for comment to the Eastern District wasn't immediately returned.

James was arrested -- after allegedly tipping police off himself to his location -- on April 13 in the East Village, more than 24 hours after his alleged crimes shook the city, already grappling with a spike in violent subway incidents, to its core.

The suspect made his first appearance in Brooklyn federal court later that same day the day, as federal, state and local law enforcement agencies worked to piece together the details of the 62-year-old Black man’s life. He was ordered held without bail.

James didn't speak at the hearing other than to nod when a judge asked if he understood the federal charge against him. He waived his rights to a preliminary hearing and was ordered to undergo a psychiatric evaluation at the time.

"The defendant’s attack was entirely premeditated. The day before the shooting,
the defendant picked up a U-Haul in Philadelphia, Pennsylvania, which he drove over the Verrazzano-Narrows Bridge and into Brooklyn in the early morning hours of April 12," prosecutors said in the detention memo. "The defendant came to Brooklyn prepared with all of the weapons and tools he needed to carry out the mass attack."

Those items, according to court papers, included a Glock 17 pistol bought by the suspect, a container with gasoline, a torch and fireworks with explosive powder. All were later found on the platform at the 36th Street and Fourth Avenue subway station.

Law enforcement officers recovered a stockpile of weapons and ammunition from other locations allegedly controlled by James, prosecutors said. They found an empty magazine for a Glock handgun, a taser, a high-capacity rifle magazine, and a blue smoke canister in the apartment where he stayed before traveling to Brooklyn. They also found a propane tank, pillow and chair in the U-Haul linked to the scene. The propane was being used with a heater, according to a senior law enforcement official.

From James' storage unit, investigators recovered 9mm ammunition, a threaded 9mm pistol barrel that allows for a silencer or suppresser to be attached, targets, and .223 caliber ammunition, used with an AR-15 semi-automatic rifle.

As for the gun he had on the subway to allegedly carry out the attack, investigators said he had three magazines that held 30 rounds each — up to 90 bullets in all. Some officials also said they think one smoke grenade might have accidentally been set off prematurely on that train, prompting James to allegedly begin shooting.

Read the full detention memo below.

Pictures: Multiple People Hurt in Brooklyn Subway Shooting