The Supreme Court reasoned that the Due Process Clause of the Fourteenth Amendment made the right to be able to compel defense witnesses to testify necessary for a defendant's "due process" rights to fair proceedings, which applies to the states.
The Supreme Court reasoned that the Due Process Clause of the Fourteenth Amendment required this right of being able to compel defense witnesses to testify as essential to having a fair trial. In this way, it was necessary for a defendant's "due process" rights, the right to have fair proceedings, which is a rule that applies to the states.