Lawyers for Tom Petters are asking a federal appeals court for a new trial.The Minnesota businessman was convicted last December of running a $3.7 Billion Ponzi scheme.In papers sent Friday to the 8th circuit court of appeals, they say Petters' accusers ``were amongst the most prolific liars, forgers and con artists in recent memory.''The defense contends it was not allowed to present the jury with full evidence about a key prosecution witness.They say it was Larry Reynolds who masterminded the fraud within Petters' company, without Petters' knowledge.