A onetime Pennsville police officer targeted in  a federal child-pornography investigation faces up to 20 years in prison, after admitting today that he tried to derail it.

Robert Waterman, 31, of Wrightstown, pleaded guilty in Camden to a count of obstruction of a federal investigation, admitting that he destroyed a computer hard drive.

According to New Jersey U.S. Attorney Paul Fishman's office, FBI agents told Waterman on March 4, 2010, that he was under investigation for child pornography possession.

Prosecutors say that Waterman admitted taking the hard drive from his garage after the interview, placing it in his patrol car, and destroying the printed circuit board in the car while parked at police headquarters in order to block the probe.

The offense also carries a possible fine as high as $250,000. Waterman's sentencing is scheduled for April 18. He's been released on a $100,000 personal recognizance bond.