Prosecutors allege that, in January, Thomas Gilbert shot and killed his hedge-fund manager father—reportedly over a drop in his allowance—and tried to make it look like a suicide. At a hearing in State Supreme Court this month, his defense argued that Gilbert is not fit to stand trial.

In September, the New York Times reports, after reviewing medical records, two court-appointed psychiatrists determined that Gilbert was too mentally ill to stand trial. “He suffers from a disorder that I would characterize as psychotic,” one of the psychiatrists, Dr. Daniel Mundy, testified. “I would be treating him with an antipsychotic.”

(A defendant can be found to suffer from mental illness and still stand trial so long as he or she can understand court proceedings and assist their lawyers. If the court rules that Gilbert is not competent—that is, that he can’t assist in his own defense—he will be hospitalized and treated until he is found sane, then tried.)

From the Times:

A psychiatrist in South Carolina, Dr. Kevin H. Spicer, had noted that Mr. Gilbert had a persistent delusion that he was being contaminated by other people and thought he could ward off the illness by spitting and pointing a finger inside his pocket. Dr. Spicer put Mr. Gilbert on antipsychotics and warned his parents that their son might be schizophrenic, a diagnosis his parents resisted, the records showed.

A series of doctors who later treated him in Princeton and New York City had documented similar bizarre beliefs. He repeatedly expressed delusions that people were “stealing his soul” or “infecting his mind,” according to the records. He also said enemies were hacking his telephone and computer and were airing skits on “Saturday Night Live” to mock him.

Still, the physicians’ diagnoses were not consistent, with some pointing to schizophrenia and schizo-affective disorder, and others saying he suffered from depression, anxiety and obsessive compulsive disorder.

Gilbert’s lawyer, Alex Spiro, has “signaled” that he will mount an insanity defense, according to the Times. Spiro, the East Hampton Star reports, has defended Gilbert several times before—on his late father’s dime.

However, after speaking with Gilbert for a half-hour last month, Dr. Stuart Kirschner, a forensic psychologist hired by the Manhattan district attorney’s office, testified that Gilbert was competent to stand trial. From the Star:

The lead prosecutor, Craig Ortner, called Dr. Stuart M. Kirschner, their expert witness, first. Dr. Kirschner told the court that while Mr. Gilbert Jr. might be “delusional,” it would not prevent him from assisting his lawyer in his defense. “He doesn’t have a long history of psychosis,” the doctor said. He described Mr. Gilbert as having “above-average intelligence.”

A video was played for the court of Dr. Kirschner’s interview with the defendant, who appeared calm. The psychologist was asked during cross-examination if he did not find that Mr. Gilbert’s demeanor demonstrated a “flat affect,” which would be a sign of mental illness. “No,” he answered. “I saw a sadness in Mr. Gilbert, not a flat affect.”

In the two years before his father’s death, the Times reports, Gilbert became increasingly more violent:

Mr. Gilbert’s behavior worsened dramatically in fall 2013, when he attacked Mr. Smith outside the rowhouse they shared in Williamsburg, court records show. The Brooklyn district attorney’s office dismissed an assault charge after Mr. Gilbert agreed to anger management counseling, two people with knowledge of the case said. Both discussed the disposition on the condition of anonymity because the case was sealed.

Mr. Gilbert’s feud with the Smith family didn’t end, however. In January 2014, he stole a flag from the Smith family mansion in Sagaponack and was charged with petit larceny, Southampton Town police said.

That spring, he was banned from the exclusive Maidstone Club in East Hampton after he threatened to kill a locker room attendant, according to testimony at the hearing.

On Labor Day 2014, he violated a protection order and approached Mr. Smith on Sagg Main Beach, the Southampton Town police said. Two weeks later, the Smiths’ estate was engulfed in fire at the hands of an arsonist.

Detectives picked up Mr. Gilbert on Sept. 18, 2014, regarding the order of protection and to question him about the fire, law enforcement officials said. He was never charged in connection with the fire.

The Times also interviewed an ex-girlfriend (“19 years older than Thomas Gilbert Jr.”) of Gilbert’s, Anna Rothschild, who dated him on and off throughout last year. “He was a total health nut,” she said. “He was extremely introverted, but he was so good-looking that no one cared.”

Photo via AP Images. Contact the author of this post: brendan.oconnor@gawker.com.