A Pine Bluff alderman convicted in an extortion case in federal court wants his conviction thrown out. Jack Foster claims prosecutors failed to prove he committed a crime eligible for prosecution in federal court. A jury convicted Foster of an extortion-related count in September. Prosecutors say he accepted money from an undercover agent and an investor in exchange for a zoning vote. Foster was indicted by a federal grand jury last year along with then-Alderman Billy Freeman. Freeman has pleaded guilty in the case. After his conviction, Foster refused to relinquish his city council seat and continued as a Pine Bluff mayoral candidate. He finished sixth in a field of eight in the November second 2 general election. He says he should not have to resign from the council until his appeals are exhausted.