By Natasja Sheriff

NEW YORK (Reuters) - A prosecutor testifying at the trial of a man accused of the 1979 murder of a New York City boy on Tuesday defended a decision not to tape hours of police questioning of the suspect, saying it was common practice at the time not to record such interviews.

Pedro Hernandez, 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.

About six hours of the interview, before he confessed, were not recorded.

Hernandez's attorneys say his confession was coerced and that their client is mentally ill 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.

Testifying at Hernandez' trial in state Supreme Court in Manhattan, Assistant New York District Attorney Armand Durastanti said he watched Hernandez being questioned by police in an interview already underway when he arrived.

He testified that he decided not to record the interview midway on grounds that it may seem disjointed or nonsensical.

"Back in the old days, we never recorded initial interviews between police officers and suspects," Durastanti testified.

Now, however, there are a number of pilot programs at police precincts to record interviews, he said. 

Recording of the 2012 interview began after Hernandez started making a confession and was read his rights, the prosecutor said.

Defense attorneys for Hernandez, 54, have suggested that police and prosecutors pressured his confession and prompted him with details of the case that he would not have otherwise known.

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

He told police in his videotaped confession that he lured the boy into the grocery store where he worked with the offer of a soda.

Patz has never been found. He was declared dead in 2001.

Hernandez' 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.

(Reporting by Natasja Sheriff; Editing by Ellen Wulfhorst and Eric Beech)