Issue Specialization as a Variable in Opinion Assignment on the U. S. Supreme Court

Is issue specialization another variable in opinion assignment on the United States Supreme Court? I examined the civil liberties cases of the Warren Court and found that issue specialization was usual and commonplace on the Court. It was present, however, in narrow issues (such as right to counsel) and not in civil liberties in general or even in somewhat broader issues (such as criminal defendant cases). I also discovered that Chief Justice Warren tended to select as issue specialists justices who had the same or similar ideological views as himself.