What is the test for a sentence that is disproportionate to the crime committed under the Eighth Amendment?

The final clause prohibits not only barbaric punishments, but also sentences that are disproportionate to the crime committed. Solem v. Helm, 463 U.S. 277, 284, 103 S.Ct. 3001, 3006, 77 L.Ed.2d 637 (1983). A court's proportionality analysis under the Eighth Amendment should be guided by objective criteria, including (i) the gravity of the offense and the harshness of the penalty; (ii) the sentences imposed on other criminals in the same jurisdiction; and (iii) the sentences imposed for commission of the same crime in other jurisdictions. Id. at 292, 103 S.Ct. at 3011.