Is severance the default remedy when part of a warrant is valid, or does the Fourth Amendment also require that the valid sections make up 'the greater part of the warrant'?

QUESTIONS PRESENTED Because the exclusionary rule should be “our last resort, not our first impulse,” Hudson v. Michigan, 547 U.S. 586, 591 (2006), all the Courts of Appeals have held that the valid parts of a warrant may be severed from the invalid parts of a warrant. Many courts favor severance as the default remedy. Some courts, however, impose an additional condition before severance can apply: that the valid portion “make up the greater part of the warrant.” United States v. Sells, 463 F.3d 1148, 1150 (10th Cir. 2006). This split leads to very different outcomes. Here, the search of respondents’ home was conducted pursuant to a partially defective warrant, and a divided Missouri court upheld the suppression of all the seized evidence after finding that the valid parts did not make up the “greater part” of the warrant. In conducting its analysis, the lower court also committed two additional errors. It extended the “particularity” requirement to the warrant’s showing of probable cause. And it did not consider whether the exclusionary rule applied when the police officer checked a box on the warrant form based on a legal mistake, and the issuing judge signed off on it. I. Is severance the default remedy when part of a warrant is valid, or does the Fourth Amendment also require that the valid sections make up “the greater part of the warrant”? II. Does the particularity clause apply only to “the place to be search” and “the things to be seized,” or does it extend to the “probable cause” requirement? III. Does the exclusionary rule apply when the issuing judge signs off on the officer’s legal mistake in filling out a warrant form?