TROY – A registered sex offender's failure to report signing up for Facebook led to the unusual case of Rensselaer County District Attorney Joel Abelove suing North Greenbush Town Justice Stephanie Piel.The lawsuit in Rensselaer County State Supreme is one Abelove, Piel and her attorney won't comment on. And it's a case that court observers and attorneys said they haven't seen happen before at the county courthouse.