[1][2] "The Fourth Amendment contains no provision expressly precluding the use of evidence obtained in violation of its commands,"[3] but in Weeks v. United States (1914) and Mapp v. Ohio (1961), the Supreme Court created the exclusionary rule, which generally operates to suppress – i.e. prevent the introduction at trial of – evidence obtained in violation of Constitutional rights.

The exclusionary rule generates substantial social costs, which sometimes include setting the guilty free and the dangerous at large.

[8] Bennie Herring drove to the Coffee County, Alabama, sheriff's department to check on a pickup truck that had been impounded.

He claimed that the arrest was unlawful as a result of an invalid/recalled warrant ("failure to appear", issued by neighboring Dale County, Alabama), a motion denied by the trial court.

While noting that there had not necessarily been a constitutional violation in the case, the Court accepted for the sake of argument Herring's contention that there had been.

On that stipulation, the court held that the exclusionary rule did not apply to a search that resulted from isolated and attenuated police negligence, holding that "[t]o trigger the exclusionary rule, police conduct must be sufficiently deliberate that exclusion can meaningfully deter it, and sufficiently culpable that such deterrence is worth the price paid by the justice system."

"[W]hen police mistakes are the result of negligence such as that described here, rather than systemic error or reckless disregard of constitutional requirements," the Chief Justice wrote, "any marginal deterrence does not 'pay its way.'"

She wrote that "the exclusionary rule provides redress for Fourth Amendment violations by placing the government in the position it would have been in had there been no unconstitutional arrest and search.