A North Jersey man convicted of killing a cabdriver in 2003 will get a new trial after the state Supreme Court ruled yesterday that it was improper for police to question him before telling him he had the right to remain silent.

The unanimous court ruled in favor of Michael A. O'Neill in the case that was a test of the "question-first, warn-later" technique some investigators use to tell suspects of their Miranda rights only after they have incriminated themselves.

The U.S. Supreme Court has considered a similar case, but has not settled whether the technique is acceptable under the U.S. Constitution.

But the New Jersey court was firm in its stance that the technique is inappropriate under the state constitution, which offers crime suspects additional rights.

"No rule of law is better understood by law enforcement officers than the duty to advise a suspect subject to custodial interrogation of his right to remain silent and his right to the assistance of counsel," Justice Barry T. Albin wrote. "Indeed, the term 'Miranda rights' is now so familiar that it is part of our popular vocabulary and culture."

Two days after cabdriver Luis A. Tenezaca was shot to death in Kearny, N.J., O'Neill was arrested in an unrelated case. Detectives knew he had a gun, however, and asked him about his whereabouts at the time the cabbie was killed.

After 20 minutes of questioning in a holding cell, detectives moved O'Neill, of Harrison, N.J., to a commander's office and continued the interrogation for more than an hour.

During that time, O'Neill said he intended to lure a cabdriver to a place where two other people would rob him. Only after he said that did detectives read O'Neill his Miranda rights.

After that, he gave a taped statement in which he repeated much of the same information.

At his trial, prosecutors used only statements O'Neill made after he was explained his rights. It was enough to convict him of murder.

An appeals panel upheld the conviction. But the Supreme Court found that after implicating himself once, it would have been difficult for O'Neill to reverse course.

Stephen Kirsch, the assistant deputy public defender who argued the case, said the ruling sends a strong message to investigators in New Jersey.

Reading suspects their Miranda rights "is not supposed to be a game where you drop them in," he said.

It's not clear when a new trial might take place, or whether O'Neill might accept a plea deal.