The former headmaster of an elite Delaware prep school is challenging his child pornography conviction.

Christopher Wheeler was sentenced to 50 years in prison after being convicted on 25 counts of dealing in child pornography.

Wheeler is a former headmaster at Tower Hill school in Wilmington, whose graduates include DuPont Co. CEO Ellen Kullman, U.S. Sen. Chris Coons and television personality Dr. Oz.

Wheeler waived his right to a jury trial after a judge denied a defense motion to suppress evidence seized by police.

In court papers Monday, Wheeler's attorney said that authorities used possible witness tampering as a pretext to obtain warrants allowing them to search Wheeler's computers for child pornography and that there was no evidence Wheeler viewed any images of child porn or knew they even existed.