In prosecution on drug conspiracy charge, Dist. Ct. did not err in admitting several wiretapped telephone conversations involving defendant’s alleged co-conspirators. Dist. Ct. could properly find under preponderance of evidence standard that govt. established requisite foundation for admitting such statements where: (1) defendant did not dispute that drug conspiracy existed or that said statements concerning plans for drug sales were made in furtherance of said conspiracy; and (2) record showed, and jury found, that defendant had joined said conspiracy. Fact that many co-conspirator’s statements were made prior to defendant’s joining of conspiracy was irrelevant, where defendant had essentially adopted previous acts and declarations of his co-conspirators when he joined conspiracy.