What is the burden of persuasion against the government?

Although the government retains the burden of persuasion, a defendant must introduce some evidence contrary to the presumed fact in order to rebut the presumption. Martir, 782 F.2d at 1144. Once a defendant introduces rebuttal evidence, the presumption, rather than disappearing altogether, continues to be weighed along with other factors to be considered when deciding whether to release a defendant. Id.; see also United States v. Jessup, 757 F.2d 378, 382-83 (1st Cir.1985) (rejecting "bursting bubble" approach).