David Tarloff, 39, was arraigned on charges of second-degree murder, second-degree attempted murder and first-degree assault. He claimed that his court-appointed lawyer, Reginald Sharpe, was "not an attorney."
Acting Supreme Court Justice Ruth Pickholz ordered that Tarfoff have a psychiatric evaluation before being brought back to court Feb. 23.
CBS News affiliate WCBS reports that according to police, the motive was murder, but the doctor was not his intended target.
The defendant's brother, Robert Tarloff told WCBS that he was not prepared to make a statement, but later told reporters off camera that his family had tried to keep David institutionalized, but that he kept getting released.
Tarloff will once again be hospitalized, this time at Bellevue Hospital's psychiatric ward for criminals. He will undergo psychological evaluation to determine if he's mentally competent to stand trial.
Tarloff was arrested Saturday after investigators matched his palm prints with those at the bloody crime scene where therapist Kathryn Faughey was killed Tuesday evening. Police said he told investigators he planned to rob another psychiatrist he said had institutionalized him 17 years ago, but ended up in Faughey's office.
Tarloff made incriminating statements during a 35-minute interrogation, Police Commissioner Raymond Kelly said. But the commissioner declined to say whether Tarloff had confessed.
Police said it remained unclear why Tarloff would have attacked Faughey, who was slashed 15 times. A psychiatrist who worked nearby, Dr. Kent Shinbach, came to Faughey's aid and was badly injured.
During questioning, Tarloff said he planned to rob Shinbach and leave the country with his mother, who is in a nursing home but until recently had lived with him, police said.
Kelly couldn't confirm whether Tarloff was ever Shinbach's patient or whether he'd met Faughey.
Tarloff had been arrested earlier this month on charges of punching a security guard in the face after being asked to leave St. John's Episcopal Hospital in Queens, Kelly said. It wasn't clear why Tarloff had been at the hospital.
Police said they matched his prints from the Feb. 1 arrest with three found on a suitcase - filled with adult diapers and women's clothing - left near the basement door where the killer escaped. Also found was a smaller bag with rope, duct tape and knives not used in the attack, police said.
One neighbor who has known the Tarloff family for decades, Phyllis Zicherman, said Tarloff had seemed down lately, but she was stunned to hear he was a suspect. "He had problems, but he was never violent," she said.
Tarloff had gone to college but did not graduate and was unemployed, neighbors said.
Investigators said the pudgy, balding, middle-aged killer arrived around 8 p.m. Tuesday, telling the doorman he had an appointment with Shinbach. Then he sat in the waiting room with one of Shinbach's patients until the patient went into his office around 8:30 p.m., police said.
Sometime after that, the killer entered Faughey's office and attacked her. Shinbach came to her aid but was assaulted, pinned behind a chair and robbed of $90. The killer then tried to attack Shinbach's patient, but she fended him off and he fled, according to police.
Shinbach was taken to New York-Presbyterian Hospital/Weill Cornell Medical Center with slash wounds on his head, face and hands. Kelly said the psychiatrist was released Saturday.
Kelly said investigators worked around the clock on blood and DNA samples from the scene, and three witnesses, including Shinbach, picked Tarloff out of a lineup.
Police examined every possible lead, combing through surveillance footage and removing evidence from the slain therapist's office. Kelly said Saturday the suspect was seen on surveillance tapes about an hour and a half before the slaying walking the same escape route he would later use.