Updated

A judge declared a mistrial Tuesday after jurors said they couldn't reach a verdict in the case of a mental patient who slashed a New York City psychotherapist to death with a meat cleaver.

The defense didn't dispute that David Tarloff killed Kathryn Faughey in February 2008, but defense lawyers said he was so psychotic that he couldn't tell what he was doing was wrong.

The Manhattan district attorney's office said Tarloff carried out a deliberate plan and understood it was illegal. It plans to retry the case.

Tarloff told authorities he set out to rob Faughey's officemate, encountered her instead and thought she was evil. Tarloff envisioned getting money from the holdup to whisk his sick mother away to Hawaii.

It was the jury's 10th day of deliberations.

"It's very disappointing for us, but we will be back until we get justice in this case for our sister," said Owen Faughey, one of the victim's brothers.

"We'll do whatever it takes, and we will see justice, I'm sure of that," said another, Michael Faughey.

Faughey, 56, specialized in helping people with relationships. She'd never met Tarloff, let alone treated him.

"We're terribly disappointed that the jury could not reach a unanimous decision," said defense attorney Frederick Sosinsky. "We believe this was a very powerful case for a `not responsible' verdict, as rare as those verdicts might be."

Tarloff, now 45, was diagnosed with schizophrenia during his college years. He has been hospitalized more than a dozen times, recounted seeing "Satan" spelled out in his mind and the "eye of God" on the kitchen floor and viewed pieces of paper on the street as a special message from God, according to court papers. His brother testified that he once came to find Tarloff naked and throwing eggs on the wall.

For years, his relatives tried unsuccessfully to get him to stay in mental hospitals or adult homes, but he left them.

After his mother moved from the Queens apartment they shared to a nursing home in 2004, Tarloff became convinced she was being mistreated and determined to get her out.

He hit upon a scheme to get the money: Hold up Dr. Kent Shinbach, the psychiatrist who'd had first him hospitalized in 1991, to get the doctor's ATM code, he later told authorities.

After making a series of phone calls to find out the location and hours of Shinbach's office on Manhattan's Upper East Side, Tarloff bought a cutlery set, a rubber meat-pounding mallet and rope. He set out with those and a suitcase of adult diapers and clothes for his mother.

Faughey, who shared Shinbach's office suite, confronted Tarloff. He slashed her 15 times, fractured her skull with the mallet, seriously wounded Shinbach when he tried to rescue her, and fled.

Tarloff was not in court Tuesday and the jurors were not in court. Several jurors left declining to speak to reporters.

A few jurors stopped to talk to Faughey's three brothers and three sisters who were in court. The family could be overheard thanking them for efforts

Lawyers will be back in court May 21 for status update.