A heart-shaped note was found in argyle socks bound for Luigi Mangione: prosecutors

Luigi Mangione violated the "special treatment" he was afforded for his last court appearance when handwritten notes were concealed inside a pair of argyle socks he was allowed to wear, New York City prosecutors said Wednesday in a new court filing.

Mangione, who has pleaded not guilty to the assassination-style killing of United Healthcare CEO Brian Thompson, was given special accommodations for his "fashion needs" when he was allowed to change out of his jail-issued clothing.

A court officer was given a bag of clothing by members of the defense team.

Among the items was a new pair of argyle socks wrapped around cardboard. "Secreted in the cardboard were two personal heart-shaped notes, one addressed to an unknown person named 'Joan' and the other to Luigi stating in part "know there are thousands of people wishing you luck," the Manhattan district attorney's office said.

"In spite of this, the defendant was permitted to wear the argyle socks, which he first changed into and later changed out of because he felt that 'they did not look good.' Fortunately, the items smuggled were handwritten notes and not contraband capable of harming the transporting officers," prosecutors said.

In a letter, the defense said, "This was obviously inadvertent as one of the two heart-shaped notes was not even addressed to Mr. Mangione. The District Attorney's Office ostensibly realized the innocent nature of this event, and that it was not a genuine danger or concern, as they did not bother to alert the Court at the time."

The sartorial detail was included in a filing that responded to defense accusations that prosecutors withheld grand jury witness testimony and copies of electronic devices seized upon Mangione's arrest, in violation of discovery obligations.

Prosecutors conceded they have not provided the testimony of civilian witnesses before the grand jury because they "constituted a fraction of the testimony before the Grand Jury," comprising 4 of the 23 witnesses called. Otherwise, the DA's office said there have been ample discovery disclosures to the defense.

Meanwhile, a black backpack Luigi Mangione was carrying when he was arrested was full of items that could suggest he intended to remain on the run and, possibly, kill again, according to a newly disclosed court document.

The backpack contained a gun, a Glock magazine, 9mm cartridges and a silencer, along with a knife, phone charger, wallet, chrome drill bits, duct tape, credit cards, a Maryland drivers license, passport, Zip ties, headphones, 32GB memory device, batteries, boxer shorts, a multi-colored hat, 8 pairs of socks, a light green jacket, a parka, grooming items, toothbrush, computer and handwritten notes, the document said.

The document, known as an automatic discovery form, catalogues what investigators found and what prosecutors intend to disclose to the defense. The form indicates investigators took swabs from many of the items and from a pizza box and a lemonade bottle at the Altoona Police Department.

Authorities also found receipts for items purchased at a CVS store and for registration at the hostel in New York City under the name Mark Rosario, which matches the name on a fake New Jersey driver's license Mangione allegedly carried.

As they built their case against Mangione, prosecutors listened to police radio, 911 calls, a videotaped statement and watched both surveillance and body-worn camera video, the document indicated. They also extracted data from a Motorola cell phone Mangione "dropped during flight," Mangione's iPhone and MacBook, an HP Laptop believed to be used by Mangione at an Altoona Best Buy and several memory devices.

Prosecutors also took issue with Mangione's request for a laptop while jailed.