Principles of a lower court's discretion according to SCOTUS

The decision in Beard, comparing the per curiam (unsigned) opinion in Michigan v. Fischer, Stevens and Sotomayor dissenting (opinion here); the Court swoops in to reverse the trial judge and appellate affirmation in Fischer ruling in favor of suppression motion while in Beard narrowly holds on the basis that discretion in the lower courts ought to be preserved.

Makes sense as long as one does not take into account principle too strongly.