A Whanganui man who admitted sex offences against his grandson was continuing to justify and minimise his offending, prosecutors say.
The man, whose name is suppressed to protect the name of his victim, tried to justify his offending to a pre-sentence report writer by saying it was his "duty" to teach the boy the correct sexual activities.
He was jailed in Whanganui District Court for three years and four months after admitting charges of sexual violation by unlawful sexual connection and indecent assault for offences committed over a six- to eight-week period in 2008 and 2009.
The man was arrested after turning himself in to police in February 2011 to admit 10-12 offences, the Wanganui Chronicle reported.
He told police he became "intrigued" at the boy frequently expressing himself in ways of a sexual nature.
Prosecutor Jo Woodcock said the offender's expressed remorse needed to be weighed against the attempts to the pre-sentence report writer to justify and minimise his offending.
The offender's lawyer, Mark Bullock, said his client was depressed at the time of the offending.
Mr Bullock said the man told police he was "intrigued" as an explanation and not to minimise the offending, and he was disgusted by his actions.