Accused daddy killer Thomas Gilbert Jr. refused to attend his murder trial Wednesday for the second day in a row.

The trial was delayed a half-hour while Gilbert’s lawyer, Arnold Levine, visited him in a holding cell and tried to persuade him to return to the courtroom.

“He declined and informed me that he wasn’t going to come back anymore,” Levine reported to the judge.

Gilbert, 34, faces a top charge of second-degree murder for shooting his dad, Thomas Gilbert Sr., in the head on Jan. 4, 2015, after his weekly allowance was slashed by $100.

The once-handsome, 6-foot-4 Princeton graduate has deteriorated in jail and appears gaunt, pale and withdrawn.

During the first four days of testimony, Gilbert alternated between barking out convoluted legal phrases and rocking softly in his chair with his eyes closed and his head bowed.

On Monday, his outbursts became so frequent and disruptive, Justice Mellissa Jackson ordered his removal from the courtroom — but allowed him to return after he assured her he’d behave.

Gilbert’s attorney has mounted an insanity defense, arguing that his client has a long history of mental illness, including diagnoses of schizophrenia and bipolar disorder, and wasn’t acting rationally when he pulled the trigger.

Assistant DA Craig Ortner has conceded that Gilbert suffers from mental illness but said the defendant understood that what he was doing was wrong when he shot his father with a .40-caliber Glock and fled.