A Des Moines man’s arrest on warrants at a Newton convenience store several weeks ago has led to a 15-year prison sentence. 43-year-old Richard Eugene Keller pleaded guilty to a class D felony charge of 3rd offense possession of a controlled substance. Two additional counts of the same charge were dismissed Monday as part of his plea agreement and sentencing by Jasper County District Court Judge Nicholas Bailey. Court records state that a Jasper County Sheriff’s Deputy, who was acting on a tip, arrested Keller on outstanding warrants at a West 4th Street South convenience store in Newton on October 24th. In Keller’s backpack, officers recovered a plastic bag with .76 grams of meth, a plastic baggie with .37 grams of marijuana, 60 servings of THC edibles, five two-ounce…..