A Big Island man who admitted having sex with an underage girl in Cambodia will have federal court officials monitoring him for the rest of his life.

A federal judge sentenced Richard David Mitchell, 61, of Waimea to a 46-month prison term that Mitchell agreed to when he pleaded guilty to a sex tourism charge last November.

U.S. District Judge David Ezra also sentenced Mitchell to lifetime court supervision after he completes his prison term and ordered him to pay $6,500 in restitution.

Mitchell admitted having sex with a prostitute who was at least 12 but less than 16 years old in August 2008.

Cambodian police arrested Mitchell after witnesses told them they saw Mitchell having sex in public with a girl they believe was 12.

Mitchell remained in a Phnom Penh prison until last August, when Cambodian officials returned him and three other Americans accused of similar crimes to the U.S.

He will not get credit for the year he spent in Cambodian custody, according to the terms of the plea agreement.