A Nelson man was today sentenced to preventive detention for a series of sex offences against girls and boys.

The mother of one of the victims of William Herbert Mortensen, 53, told the High Court at Nelson this morning she hoped he would "rot in jail forever".

Mortensen had admitted a charge of sexual violation by unlawful sexual connection with a male between 12- and 16-years-old, a charge sexual violation by unlawful sexual connection with a girl under 12-years-old, a charge of indecent assault on a boy under 16-years-old, and four charges of performing an indecent act on girls under 12-years-old.

He had also admitted six charges of knowingly making an objectionable publication, 12 charges of knowingly supplying an objectionable publication, three representative charges of possession of an unlawful publication, three charges of theft, and three charges of indecency with an animal.

The victims included girls and boys aged between eight and 15, and three dogs.

The mother of one of the victims, aged eight at the time of the offending, gave a victim impact statement to the court before sentencing.

She said she had regarded Mortensen as a friend and confidant, and now hoped "all the karma in the world" would catch up with him.

"If I had my way he would rot in jail forever."

Justice Stephen Kos said Mortensen had been in prison in the 1990s on similar charges, but despite receiving counselling, once he left jail he became obsessed with internet pornography, and returned to his old ways.

Mortensen had a high risk of reoffending, Justice Kos said.

He sentenced him to preventive detention, with a minimum prison term of five and a half years.

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