WASHINGTON—Two Supreme Court justices told a House subcommittee Monday that the American criminal-justice system is too harsh, locks up too many people for too long and does so at an ultimate cost to public safety.

“This idea of total incarceration just isn’t working,” Justice Anthony Kennedy said, speaking at a House Appropriations Committee hearing to discuss the Supreme Court’s annual budget request. In many instances, he said, it would be wiser to assign offenders to probation and other supervised release programs.

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