The United States Supreme Court may reach the federal question on review, unless the state court’s opinion contains a “plain statement” that its decision rests upon adequate and independent state grounds.  The “plain statement” rule applies regardless of whether the disputed state-law ground is substantive or procedural.  Therefore, the mere fact that a federal claimant failed to abide by a state procedural rule does not prevent the United States Supreme Court from reaching the federal claim.[i]

The court will accept as the most reasonable explanation, that the state court decided the case the way it did because it believed that federal law required it to do so when:

• the state court decision appears to rest primarily on federal law, or to be interwoven with the federal law; and
• the adequacy and independence of any possible state law ground is not clear from the face of the opinion.

If a state court chooses merely to rely on federal precedents as it would on the precedents of all other jurisdictions, then it need only make clear by a plain statement in its judgment or opinion that the federal cases are being used only for the purpose of guidance.  The court will not undertake to review a state court decision, if the decision indicates clearly and expressly that it is alternatively based on bona fide separate, adequate, and independent grounds.[ii]

[i] Harris v. Reed, 489 U.S. 255 (U.S. 1989)

[ii] Mich. v. Long, 463 U.S. 1032 (U.S. 1983)