A Manhattan judge ruled that the Princeton grad who allegedly shot dead his millionaire hedge-fund dad is mentally fit to proceed to trial.

“Despite the competing testimony of the experts in this case, the court finds the defendant competent to stand trial,” wrote Justice Melissa Jackson of defendant Thomas Gilbert Jr. in a decision issued Monday in Manhattan Supreme Court.

Previously, court doctors found Gilbert Jr., 31, unfit and prosecutors moved to challenge those findings, hiring their own expert Dr. Stuart Kirschner to conduct an evaluation.

Kirschner found Gilbert Jr. fit, which triggered the one-week hearing.

The failed stock trader allegedly murdered his dad Thomas Gilbert Sr., the founder of hedge-fund Wainscott Capital, for cutting his allowance by $200.

In the decision, Jackson described Gilbert Jr. as an atypical defendant.

“[Gilbert Jr.’s] appearance alone is remarkable in a criminal courtroom: a graduate of the most exclusive schools on the East Coast, with a degree from Princeton University, the defendant stands over six feet tall, blond and blue-eyed,” she wrote.

The judge’s task was to determine the limited issue of whether the once-avid surfer is able to understand the proceedings and assist in his own defense.

She wrote that his decision not to be present for a majority of the hearing was a reasonable one given the detailed testimony about his psychiatric history, including diagnoses of schizophrenia and obsessive compulsive disorder.

“Clearly, there were personal and embarrassing subjects being openly discussed in a courtroom full of strangers,” she wrote. “It is understandable and rational for the defendant to have absented himself.”

Prosecutor Craig Ortner said that Gilbert Jr. might suffer from mental illness but that didn’t make him unfit.

“Mr. Gilbert may well have some form of mental illness, I’m not saying he doesn’t,” he argued during the hearing. “But there are far, far sicker people who stand trial for their crimes.”

Defense lawyer Alex Spiro insisted that Gilbert Jr. was unable to assist in his own defense even if he didn’t act outwardly crazy.

“You don’t have to be catching butterflies in a net to be unfit,” Spiro said at the hearing.

After the judge issued her decision, Spiro said, “The bar for fitness to stand trial is so low that no matter how mentally ill a person is we too often force them into courtrooms.”

Gilbert Jr. has been held without bail since the Jan. 4 slaying of his father.