By Natasja Sheriff

NEW YORK (Reuters) - The daughter of a former grocery worker accused of murdering a New York City boy in 1979 testified in her father's defense on Monday, describing how he heard voices and had visions.

Pedro Hernandez, 54, charged with kidnapping and murdering 6-year-old Etan Patz, confessed in 2012 to police that he choked the boy, stuffed him in a box and left him in a New York alley.

Defense attorneys say Hernandez is mentally ill, concocted the confession under police coercion and suffers hallucinations.

Patz vanished as he walked alone for the first time to a school bus stop in his Manhattan neighborhood on May 25, 1979. His disappearance sparked a national movement to find missing children, with his picture one of the first to appear on milk cartons.

The defendant's daughter, Becky Hernandez, 25, testified in state Supreme Court in Manhattan that her father would talk to himself.

"I would hear him having conversations," she said. "I would sometimes ask him who was he talking to, and he would say no one, and then as soon as I was about to leave the room, he would start talking again."

When she was a child, she testified, he told her about a "lady in white," whose face he could not see, and other imaginary people.

"He said, 'Sometimes I see these people, with these really old faces, and sometimes I see them behind you,'" she said.

Appearing nervous, Hernandez smiled at her father from the witness stand.

She also said her father recounted his police confession to her in 2012, and had never mentioned the case before.

"'I choked him, and I cut him up in tiny little pieces. I put him in a bag, he was still breathing, then I put the bag in a box and I put it in an alley,'" she quoted him as saying.

Defense attorneys say his story is filled with contradictions, such as Hernandez's saying he cut the boy into small pieces but he was still breathing.

Patz has not been found. He was declared dead in 2001.

Hernandez was questioned and arrested in 2012 after police got a tip that he confessed to the crime to a church prayer group in New Jersey.

His attorneys blame another man, Jose Antonio Ramos, who for many years was a prime suspect in the case. Ramos is a convicted child molester in prison in Pennsylvania.

(Editing by Ellen Wulfhorst and Mohammad Zargham)