In the case of William Duncan, Warden v. Robert E. Henry in 1994, the United States Supreme Court ruled on whether a defendant's right to counsel was violated when his lawyer did not object to an incorrect jury instruction regarding intent for burglary charges. The court held that it is not enough for a defendant to show that their attorney made an error; they must also prove that this mistake affected the outcome of their trial (the "prejudice" requirement). In this case, Robert E. Henry failed to meet this burden because he could not demonstrate how his lawyer’s failure had prejudiced him or influenced the verdict against him. Therefore, even though there was indeed ineffective assistance from his counsel due to lack of objection over wrong instructions about intent in burglary law given by judge during trial proceedings, it didn't constitute grounds for reversal as per Strickland test which requires both deficient performance and prejudice caused by such deficiency.

In the dissenting opinion for William Duncan, Warden v. Robert E. Henry, Justice Scalia disagreed with the majority's interpretation of "clearly established Federal law" in relation to habeas corpus petitions under 28 U.S.C §2254(d)(1). He argued that a federal court should not grant a state prisoner’s application for writ of habeas corpus on the basis of an unreasonable application of clearly established federal law unless it is clear beyond any possibility for fairminded disagreement that it is incorrect. In this case, he believed there was room for reasonable disagreement about whether or not Mr. Henry's Sixth Amendment rights were violated when his attorney failed to object to potentially prejudicial comments made by the prosecutor during trial. Therefore, he felt that granting Mr.Henry's petition was inappropriate and set a dangerous precedent.