Before sentencing someone in a capital case, jurors are routinely instructed to consider both factors that argue in favor of the death penalty and those that argue against it.
But if jurors find such factors equally balanced, should the guilty person get the death penalty?
That is the question at the center of a Kansas capital case that the US Supreme Court is set to hear Tuesday.
The case is important because it could force as many as a dozen states to rewrite their death-penalty statutes and make it more difficult to impose a capital sentence.
In addition, the case provides a window into how the new lineup of justices on the Supreme Court will approach capital cases following the departure of Justice Sandra Day O'Connor. She was a swing vote in death-penalty cases.
The case, Kansas v. Marsh, was originally argued at the high court on Dec. 7. It was set for reargument after the arrival of Justice O'Connor's replacement, Samuel Alito. The rescheduling of the case suggests that the justices were sharply divided over the issue and that Justice Alito may be in a position to cast the deciding vote.
The Eighth Amendment requires that in capital cases jurors make an individual assessment of aggravating and mitigating factors for a death sentence. The Supreme Court has generally left it to the states to decide how that assessment is to be carried out.
"So long as the defendant can present his mitigating evidence and the sentencer considers it, the formula for decision is a matter of state law," says Kent Scheidegger, a death penalty expert at the Criminal Justice Legal Foundation in Sacramento, Calif., in a friend-of-the-court brief.
Many states require that jurors may impose a death sentence only when aggravating evidence outweighs the mitigating evidence. But not all states have adopted that approach.
The Kansas law required a death sentence whenever a jury determined that the aggravating circumstances were "not outweighed by any mitigating circumstances."
That word choice left open the hypothetical possibility that jurors who gave equal weight to aggravating and mitigating factors would, in effect, have the decision to impose a death sentence made for them by the statute.
The Kansas Supreme Court ruled that the possibility of such an outcome violated constitutional protections against cruel and unusual punishment. The ruling invalidated the death penalty statute in Kansas and thus undermined all 12 pending capital murder cases in the state.
Rebecca Woodman of the Capital Appellate Defender Office in Topeka is arguing the case on behalf of Michael Lee Marsh II, whose death sentence was overturned by the Kansas Supreme Court.
She says the Eighth Amendment requires a careful, individual assessment by jurors of the defendant and the crime before any death sentence may be imposed. "When a jury is in equipoise regarding the aggravating and mitigating features of a case, it is by definition unable to reach any conclusions about the defendant as a uniquely individual human being," Ms. Woodman writes in her brief to the court.
Such an approach, she says, "flouts the Eighth Amendment requirement of individualized capital sentencing."
Kansas has not embraced a presumption in favor of death, countered Kansas Attorney General Phill Kline in the original Supreme Court oral argument in December.
"We are dealing with a hypothetical that we believe does not exist in jury deliberations," Mr. Kline said. "A juror steps back and decides whether they can live with the decision that is before them and then decides whether the death penalty is warranted."
He added, "Kansas law leads them to that reasoned moral decision."
A decision in the case is expected by late June.