The Supreme Court made it clear as early as 1933 that simply officers acting pursuant to a warrant does not insulate evidence seized from being suppressed if the facts presented are deemed insufficient by a reviewing court to establish probable cause (Nathanson v. United States). The principle that a warrant can be challenged after its issuance was later relied upon by the Court to invalidate arrest warrants as well as search warrants. After Mapp V. Ohio made the exclusionary rule applicable to the States, it was similarly relied upon to strike down warrants in State cases. In Rugendorf v. United States, the Court held that inaccurate information in an affidavit which is not necessary to a finding of probable cause and which does not impinge upon the integrity of the affiant will not cause a warrant to be invalidated. In Franks v. Delaware (1978), the Court made it clear that only where the defense has proof that the affiant lied or acted with a reckless disregard for the truth with respect to some material statement in the affidavit will a hearing regarding such be required. A deliberate falsehood by a nonaffiant, fellow officer may fall within the Franks rule, but an informant's misrepresentation will have no effect on the validity of the warrant. To be guilty of 'reckless disregard for the truth,' the officer must have entertained serious doubt as to the truth of the information inserted in the affidavit. The post-Franks decisions express due regard for the confidentiality of informants, but officers should note that courts may require an in camera hearing to ensure the existence of the informant and the fact that the officer has not misrepresented the informant's information. Endnotes and a chart are included.