LAWYERS defending Manuel Noriega against drug smuggling charges open their case this week and are expected to shift blame from the deposed Panamanian dictator to smugglers involved in the arms trade with Nicaragua's Contra rebels.As General Noriega's trial enters its 14th week, the defense is to begin presenting its case today, with opening statements by attorneys Frank Rubino and Jon May. Noriega is charged with 10 counts of cocaine racketeering, conspiracy, importing, and distributing. Citing a gag order by US District Judge William Hoeveler, the defense has declined to outline its case. But it is expected to try to show that although Noriega was dishonest enough to skim Panama's treasury, he was not a drug smuggler. The defense is also expected to point out that Noriega cooperated with US authorities on several occasions and will attack weaknesses in the government's case.