A discussion of the evolution of the qualified-immunity defense concludes that the U.S. Supreme Court in Harlow v. Fitzgerald attempted to articulate an objective standard that would require courts to consider only a legal question, i.e., whether the challenged conduct violated a clearly established constitutional or statutory right of which a reasonable person would have known. An examination of the Court's application of the "Harlow" standard to claims asserting a violation of the fourth amendment notes that the Court has modified the "Harlow" reasonableness standard by returning to the fact-specific reasonableness standard of Procunier v. Navarette, a pre-Harlow decision. The modified standard raises both legal and factual issues, questioning what reasonable officials would have done under the circumstances (a legal issue) and what the officials actually knew when they acted (a factual issue). This article applies the "Harlow" standard for qualified immunity to claims that police officers used excessive force during an arrest, in violation of the fourth amendment and the substantive due process component of the 14th amendment. The article concludes that even though the qualified-immunity defense is appropriately available for other fourth amendment claims, it is an unnecessary defense to a fourth amendment claim challenging the use of excessive force, because the standard for liability is identical to the standard for qualified immunity. 365 footnotes.