On the night of March 2, 1986, Walton and his two codefendants entered a bar in Tucson, Arizona, set on finding someone at random to rob, kidnap, and leave stranded in the desert.

While Walton's case was pending on direct appeal, the Ninth Circuit had ruled that Arizona's capital sentencing scheme was unconstitutional.

Walton's first contention before the Court was that "every finding of fact underlying the sentencing decision must be made by a jury, not by a judge, and that the Arizona scheme would be constitutional only if a jury decides what aggravating and mitigating circumstances are present in a given case and the trial judge then imposes the sentence based on those findings."

In Walton, however, the Court reversed this trend and upheld Arizona's "especially heinous, cruel, or depraved" aggravating factor against a similar challenge.

[3] Because judges were presumed to follow the law, they needed no guidance in finding a killing to be "heinous, cruel, or depraved" in the correct circumstances.

Second, the Arizona Supreme Court had developed a body of law that defined the words "heinous, cruel, or depraved."

For the Walton Court, these key differences meant that Arizona's "especially heinous, cruel, or depraved" aggravating factor satisfied the dictates of the Eighth Amendment.

In spite of these developments, Walton contended that the Arizona Supreme Court's definitions had still been arbitrarily applied in his case.

When the Court approved modern capital sentencing systems in 1976, it did so in part because states had undertaken this kind of proportionality review.

Justice Blackmun pointed out that "the State Supreme Court's opinions, however, will serve to narrow [a trial judge's] discretion only if that body of case law articulates a construction of the aggravating circumstance that is coherent and consistent, and that meaningfully limits the range of homicides to which the aggravating factor will apply."

In 1977, the Arizona Supreme Court took its first steps toward defining the words "heinous, cruel or depraved" by turning to dictionary definitions.

"Cruelty" focused on the "pain and distress visited upon the victim," while "heinous" and "depraved" "go to the mental state and attitude of the perpetrator as reflected in his words and actions."