An undercover investigation was conducted against a ring of crack cocaine dealers. On seven separate occasions, informants had bought a total of 124.3 grams of crack cocaine. Various buys were made and eventually a number of arrests were made, and a prosecution was instituted. Armstrong (D) along with others were indicted on charges of conspiring to possess with intent to distribute more than 50 grams of cocaine base (crack) and conspiring to distribute the same. The agents searched the hotel room in which the sales were transacted, arrested D in the room, and found more crack and a loaded gun. The agents later arrested the other respondents as part of the ring. Ds filed a motion for discovery or for dismissal of the indictment alleging that they were selected for federal prosecution because they are black. Their only support was an affidavit by a “Paralegal Specialist,” employed by the Office of the Federal Public Defender. The only allegation in the affidavit was that, in every one of the 24 § 841 or § 846 cases closed by the office during 1991, the defendant was black. The Government (P) opposed the discovery motion, arguing, among other things, that there was no evidence or allegation. The District Court ordered the Government (1) to provide a list of all cases from the last three years in which the Government charged both cocaine and firearms offenses, (2) to identify the race of the defendants in those cases, (3) to identify what levels of law enforcement were involved in the investigations of those cases, and (4) to explain its criteria for deciding to prosecute those defendants for federal cocaine offenses. P moved for reconsideration. The federal and local agents participating in the case alleged in affidavits that race played no role in their investigation. An Assistant United States Attorney explained in an affidavit that the decision to prosecute met the general criteria for prosecution. Ds' attorneys submitted an affidavit alleging that an intake coordinator at a drug treatment center had told her that there are “an equal number of Caucasian users and dealers to minority users and dealers.” Ds also submitted an affidavit from a criminal defense attorney alleging that in his experience many nonblacks are prosecuted in state court for crack offenses. The Court denied the motion for reconsideration. When the Government indicated it would not comply with the court's discovery order, the court dismissed the case. The Ninth Circuit reversed, holding that, because of the proof requirements for a selective-prosecution claim, Ds must “provide a colorable basis for believing that ‘others similarly situated have not been prosecuted’” to obtain discovery. The Court of Appeals voted to rehear the case en banc, and the panel affirmed the District Court's order of dismissal, holding that “a defendant is not required to demonstrate that the government has failed to prosecute others who are similarly situated.” The Supreme Court granted certiorari. Neither the District Court nor the Court of Appeals mentioned Federal Rule of Criminal Procedure 16, which by its terms governs discovery in criminal cases.