Luigi Mangione's NY prosecutor is Joel Seidemann, a Manhattan DA veteran described as a 'firecracker' in court

• Manhattan DA Alvin Bragg has tapped Joel Seidemann to lead the Luigi Mangione prosecution.
• His 40-year career includes prosecuting the Etan Patz murder and Brooke Astor swindle cases.
• Colleagues say he's tenacious and detail-obsessed, with an expertise in fighting psych defenses.

Former colleagues say he's detail-obsessed and relentless. One calls him "a firecracker." And they're hard-pressed to name anyone in the district attorney's office more capable of crushing a psych defense in a murder case.

Joel Seidemann is the veteran assistant district attorney who will be helming the Manhattan prosecution of 26-year-old Luigi Mangione, charged in last week's ambush shooting of UnitedHealthcare CEO Brian Thompson.

Seidemann has been prosecuting high-stakes, high-profile crimes, including homicides, for 42 years.

"I think a great deal of Joel," said Cyrus Vance, Manhattan District Attorney during Seidemann's two biggest trial wins, in the Etan Patz murder and Brook Astor swindle cases.

"He's probably tried more cases than anybody in the DA's office," said attorney Daniel Bibb, hired as a prosecutor six months after Seidemann and now in private practice.

"It's a sign, certainly, that the Manhattan DA's office is giving this their very highest priority," said veteran defense lawyer Ron Kuby.

An author and former adjunct law professor at Pace University, Seidemann does not wilt under the national spotlight that has found him and his cases over the decades.

In addressing judges and juries, he readily turns the dry language of police and medical reports into vivid sound bites.

"They didn't call for an ambulance. They didn't call for help. Rather, they stood on the street corner and laughed," he told a judge of the teen suspects in the fatal 2006 mugging of an NYU student.

"She had her hair done while her husband lay in surgery," he told another judge in 2008, arguing against bail for Barbara Kogan, dubbed the Black Widow for her pricey dark attire. (Kogan soon after pleaded guilty to her husband's 1990 contract killing.)

More than one former colleague said with affection that Seidemann lands his best lines with seeming self-awareness, sometimes peeking over his shoulder to check the courtroom audience's reaction.

Meanwhile, defense lawyers described him as a relentless adversary.

One of the few high-profile trials Seidemann has lost was the 2007 acquittal of David Lemus in a fatal 1990 shooting at the Palladium nightclub. The case was featured in a recent NBC documentary, The Sing Sing Chronicles.

Both of Lemus's lawyers called Seidemann tough but fair.

"Joel tried the best case he could, but David Lemus was innocent," attorney Jonathan P. Bach told Business Insider.

"He was a consummate professional, extraordinarily talented," agreed co-counsel Daniel J. Horwitz. "But we had the two actual killers taking the stand, and confessing to pulling the trigger."

A spokesperson for the Manhattan DA's office declined to comment on this story. Mangione's attorney in Pennsylvania, where he is fighting extradition, did not respond to repeated requests for comment. Neither did his New York attorney, Karen Agnifilo.

Mangione has been denied bail and remains held in a central Pennsylvania jail as he awaits a yet-scheduled extradition hearing.

The Etan Patz case

"Joel is fabulous — he's as experienced in that office as they go, and I don't have a bad thing to say about him," said former prosecutor Joan Illuzzi, also now in private practice.

In 2017, Seidemann and Illuzzi won a kidnapping and murder conviction in a case that held national attention for decades, 1979 disappearance of six-year-old Etan Patz.

"He's especially skilled at psych cases," said Illuzzi, noting that the Patz conviction required jurors to believe former bodega worker Pedro Hernandez had confessed to killing Patz because he was guilty, not because he was mentally unsound.

The Mangione case, should it go to trial, may also hinge on a psych defense. Longtime Manhattan attorneys told BI this week that his best hope may be going to trial on what's called an extreme emotional disturbance defense.

The Brooke Astor swindle

In 2009, Seidemann tried what may be his most high-profile case until now — the $60 million swindling of wealthy philanthropist Brooke Astor by her own son — and he called former Secretary of State Henry Kissinger to the witness stand.

The case hinged on Astor's competency to sign repeated changes to her will. Under Seidemann's questioning, Kissinger recalled to jurors how Astor, on the brink of turning 100 years old, had been so impacted by Alzheimer's that she could no longer recognize her dear friend Kofi Annan.

The then-UN Secretary General was sitting beside Astor at a 2002 dinner party at her Park Avenue co-op.

"Who is the black fellow who is sitting on the other side of me?" Kissinger recounted Astor turning to him and asking.

Seventy prosecution witnesses testified at the seven-month trial, including journalist and editor Graydon Carter, socialite Annette de la Renta, and author Louis Auchincloss. Barbara Walters teared up on the stand as she recalled Brooke's mental decline.

"He's brilliant," said former Manhattan elder-abuse prosecutor Elizabeth Lowey, who teamed up with him to win the case. "He's a firecracker."

Seidemann synthesized stacks of financial documents and scores of witness accounts, remembered Lowey, now at the fraud prevention company EverSafe.

Then he'd pluck out the richest details to create a persuasive narrative for the jury, she said.

Among those details: the son, Anthony Marshall, sailed a teak-decked yacht. Meanwhile, he was ignoring requests by his mother's nurses for no-skid socks and a stairway safety gate.

"The yacht for $920,000? He wasn't too frugal for that," Seidemann told jurors at closing arguments. "But the safety gate for two grand? Not going to happen."

Astor's nurses called Marshall's wife, Charlene, "Miss Piggy" behind her back, Lowey remembered, and Seidemann made a point of letting jurors hear that.

"I would tell Joel we can't call her Miss Piggy, even if it's in the nurses' notes, and he would say, 'Oh yes we can," Lowey said, laughing.

"He's not afraid to call it what it is," she added. "If there's anyone who can make people understand that even if you have issues with the insurance industry, you can't be a vigilante, it's Joel."

Philip C. Marshall filed the 2006 guardianship petition that led to his father's prosecution. He told Business Insider that Seidemann kept a box of Kleenex on hand for him during interviews and trial prep.

"I just remember his ability to engage and listen — his calm and intentional nature throughout this ordeal," said Marshall, founder of the Beyond Brooke campaign against elder abuse.

More than one person interviewed by Business Insider mentioned Seidemann's height, one saying, "he still has a damn good courtroom presence." Marshall noted he is not a tall man.

"But any opponent will be dwarfed by the stack of documents and evidence that he'll bring to this case," Marshall quipped.