Life and death decisions await the post-Anthony Kennedy U.S. Supreme Court as a nation long accustomed to his swing vote wonders how the court will view the death penalty and other weighty issues of crime and punishment in his wake.

The term approaches as the high court’s future makeup is suddenly up in the air, since a woman publicly came forward to accuse Trump nominee Brett Kavanaugh of assaulting her when he was 17 and she was 15. His confirmation appeared all but certain before then.

Regardless who’s sitting on the court when October arrives, two early tests await,...