The size of the Court is not specified; the Constitution leaves it to Congress to set the number of justices.

Before Powell, the Court had reversed state criminal convictions only for racial discrimination in jury selection — a practice that violated the Equal Protection Clause of the Fourteenth Amendment.

In Sorrells v. United States, 287 U.S. 435 (1932), the Supreme Court unanimously recognized the entrapment defense.

However, while the majority opinion by Chief Justice Charles Evans Hughes located the key to entrapment in the defendant's predisposition or lack thereof to commit the crime, Justice Owen Josephus Roberts' concurring opinion proposed instead that it be rooted in an analysis of the conduct of the law enforcement agents making the arrest.

Although the Court has stuck with the predisposition analysis, the dispute has hung over entrapment jurisprudence ever since.