In the 1966 case Washington v. Texas, the U.S. Supreme Court ruled that a state cannot arbitrarily deny a defendant's right to have witnesses testify on their behalf during trial, as it violates both the Compulsory Process Clause of the Sixth Amendment and Fourteenth Amendment of the Constitution. The case involved Jackie Washington who was convicted for murder in Texas court where his co-defendant Charles Fuller wasn't allowed to testify due to state laws barring testimony from alleged accomplices or co-participants in crime. The Supreme Court overturned this conviction stating that such laws are unconstitutional because they infringe upon a defendant's right to fair trial by preventing them from securing potentially favorable evidence.

In the dissenting opinion for Washington v. Texas, Justice Harlan argued that the majority's decision to extend constitutional protection to a defendant's right to have witnesses testify on his behalf was an overreach of federal power into state court proceedings. He contended that this ruling unnecessarily expanded the scope of compulsory process clause in Sixth Amendment beyond its original intent and historical understanding. According to him, it is not within the purview of federal courts or constitution to dictate how states should conduct their criminal trials or what rules they must follow regarding witness competency and testimony. Instead, he believed such matters should be left up entirely to individual states' discretion as part of their inherent sovereignty and authority over local affairs under our system of federalism.