In the 1991 case of John H. Evans, Jr. v. United States, the U.S Supreme Court ruled on an issue related to criminal law and procedure concerning a defendant's right to testify in his own defense at trial. The petitioner, John H. Evans Jr., was convicted for drug trafficking offenses after he was prevented from testifying about certain matters during his trial due to concerns over perjury charges based on prior inconsistent statements made under oath before a grand jury investigation into similar crimes committed by him and others involved in drug trafficking activities. Evans appealed this decision arguing that it violated his constitutional rights under the Fifth Amendment (right against self-incrimination) and Sixth Amendment (right to present witnesses). However, the Supreme Court upheld his conviction stating that while defendants have a fundamental right to testify in their own defense as part of their Sixth Amendment rights; they do not have an absolute or unqualified right especially when there are legitimate reasons such as preventing perjury or maintaining integrity of judicial proceedings. The court further clarified that any restrictions imposed should be reasonable considering all circumstances including nature of evidence sought to be excluded, its relevance and potential prejudicial effect if admitted among other factors.

In the dissenting opinion for John H. Evans, Jr. v United States (1991), Justice Scalia argued that the majority's decision to uphold Evans' conviction under the Hobbs Act was incorrect because it expanded the definition of extortion beyond its traditional boundaries. He contended that historically and legally, extortion required a public official to demand or solicit a bribe; merely accepting one was not enough to constitute an offense under this law. In his view, by broadening this definition without clear legislative intent from Congress, the Court had overstepped its bounds and infringed upon principles of federalism and separation of powers. Furthermore, he expressed concern about potential prosecutorial abuse resulting from such an expansive interpretation of extortion laws.