Blame it on the cream: After Miami Beach Police Detective Reinaldo Casas tested positive for cocaine, he insisted that the drug had been unwittingly absorbed into his blood through an erection-enhancing cream he applied to his genitals. His defense worked. An arbitrator this week ordered Casas, who was fired last year because of this positive drug test, be reinstated with complete back pay. "There is no evidence in the record to show that (Casas) was aware the cream contained a controlled substance," according to the arbitrator's report released Thursday. By law, Miami Beach police must comply with the ruling. At a grievance hearing, Casas testified that a buddy, Idilio Godinez, gave him the cream "with the advice that it would help him in his sexual liaisons." Godinez testified that he got the sex-enhancement cream from "an old Cuban guy" as a gift for giving him some political campaign signs. Godinez claimed he did not know what was in the cream, but had tried it himself and it worked. The substance, which resembled Vaseline, was contained in a series of unmarked purple containers and appeared to be homemade.