Key Points:

A man's "deviant sexual arousal" to saliva from young girls was behind a premeditated attack on an 11-year-old, Christchurch District Court was told today.

Jared Paul Simmonds, 28, a Blenheim vineyard worker, was jailed today for two years and eight months after earlier pleading guilty to doing an indecent act with the girl in the grounds of a Christchurch school last February 6.

He had denied a more serious charge of detaining the girl for sex, and after submissions from his lawyer Stephen Hembrow and the Crown, Judge Murray Abbott discharged him on that count under Section 347 of the Crimes Act.

Simmonds was convicted in 2005 for obtaining spittle from young girls that he planned to use for masturbation -- circumstances similar to the offending in February, the court was told today.

Referring to psychiatric reports, Judge Abbott told Simmonds it was of "serious concern" that he targeted pre-pubescent girls because he was unable to relate to females of his own age.

Simmonds' "deviant sexual arousal to saliva could be regarded as a fetish," he said.

It was "of real concern" that Simmonds found it easier to relate to children rather than adults.

Judge Abbott said Simmonds had four convictions where he had asked for or obtained spittle from young girls.

The court was told that on Last Waitangi Day this year, Simmonds stopped off in Christchurch on his way back to Blenheim from Invercargill. He'd intended to find a young girl he could get spittle from which he would use to masturbate.

Judge Abbott noted Simmonds' significant premeditation in carrying chewing gum and plastic cups to support his story that he was conducting a survey.

Simmonds had promised the 11-year-old money to co-operate with the "survey" and told her the saliva would be analysed at Christchurch Polytechnic.

He'd met her as she was taking a short-cut through the school grounds. But events turned sinister when he asked the girl if he could be her boyfriend.

When she answered in the negative, Simmonds had foot-tripped her, lay on top of her, kissing her around her neck and cheeks, then held his hand over her mouth while he simulated sex with the girl.

The school principal, who told a depositions hearing she had observed the "unlikely pairing" when she noticed them in the playground, yelled out when she saw Simmonds on top of the girl. She managed to break free and run home.

When police interviewed Simmonds in Blenheim four days later, they found in his bedroom a newspaper clipping reporting the incident.

Judge Abbott said he believed Simmonds became a police suspect because of his similar earlier offending.

He told Simmonds he had a number of "bizarre thinking processes" that would have to be addressed before he could live safely in the community.

Simmonds' frank admissions to police, a probation officer and a psychologist gave "some hope" he may end his offending.

Judge Abbott told Simmonds that he wouldn't impose a minimum non-parole period. But he warned he was "on notice" for any further offending.