LOS ANGELES (CBS) —  The conviction of a former Marine and camp counselor for sex crimes involving two teenage girls was upheld Thursday by a state appeals court.

Ross Jay Curtis claimed that a Norwalk Superior Court judge erred in admitting the testimony of two female subordinates from Camp Pendleton Marine Base about uncharged sex offenses, but a three-justice panel from California’s 2nd District Court of Appeal disagreed.

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“The common theme of defendant’s sexual misconduct was his use of position of authority to engage in sexually inappropriate activity,” Presiding Justice Norman L. Epstein wrote on behalf of the panel.

Curtis was convicted in October 2009 of two counts each of lewd acts upon a child and oral copulation of a person under 16 and one count each of sexual penetration by a foreign object and sending harmful matter, and sentenced to 12 years and eight months in state prison.

Curtis met his victims at a camp where he was a counselor.

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The charges involved girls who were 13 and 15 at the time of the crimes. Curtis — who was court-martialed and discharged in 2006 following complaints that he engaged in inappropriate sexual behavior with two female subordinates — met the two girls while he continued to volunteer as an instructor at a Junior Reserve Officers’ Training (ROTC) program after his discharge, according to the appellate court panel’s 13-page ruling.

Curtis met the 13-year-old girl in March 2006 at a three-day boot camp and engaged the girl in an online affair, then had sex with the girl in May 2006 after driving her from a career day at her middle school, according to the ruling.

He met the 15-year-old girl in March 2007 while the 10th-grader was attending a three-day ROTC boot camp at Joshua Tree and had sex with her in his tent, the justices noted in their ruling.

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