A Hawai'i Air National Guardsman and former karate instructor has been sentenced to 10 years in prison for trying to get a 14-year-old girl to have sex with him.

A judge sentenced Matthew Lewis to the mandatory term Tuesday, two months after a jury found him guilty of child enticement.

Lewis was arrested in 2008 after making contact online with someone he thought was an underage girl and arranging to meet her for sex.

His contact was actually an undercover police officer.

Lewis' attorney questioned the fairness of the sentence, saying his client never intended to go through with the encounter.

The prosecutor said the sentence is appropriate because Lewis exposed himself online, had online chats of a sexual nature and arranged the meeting.