In Brown v. Payton (125 S.Ct. 1432 [2005]), the U.S. Supreme Court heard an appeal from a Californian defendant who argued that a combination of bad jury instructions and prosecutorial error prevented the jury from considering mitigating evidence in his first-degree murder trial.

The jury in the California trial had found William Payton guilty of first-degree murder with a special circumstance when he raped and stabbed to death a fellow resident at a boarding house. After his arrest, Payton spent almost two years in prison during which time he studied the Bible, became a "newborn Christian" and exerted a positive calming influence on other inmates.

At the penalty phase of Payton's trial, the defense attorney relied heavily on Payton's post-crime behavior, arguing that Payton's new commitment to Christianity was a mitigating factor to be considered against the aggravating factors that the prosecuting attorney raised, including prior convictions for a drug felony and for rape and a propensity for sexual mistreatment of women.

Although the jury applied California's then-current catch-all "K factor" instruction, which directs jurors to consider "...any other circumstance which extenuates the gravity of the crime even though it is not a legal excuse for the crime" (Cal.Penal Code Ann. ß 190.3 [West 1988]), it still recommended the death penalty.

A sufficient charge?

Payton appealed, arguing that the K instruction did not specifically allow jurors to consider his post-crime conduct as mitigation of the offense. At trial, the prosecuting attorney erroneously told the jury during closing arguments that Payton's post-crime religious conversion, which occurred conveniently after the homicide, did not constitute mitigation. The trial court did not issue an instruction to the contrary and instead considered its K charge sufficient to allow the jury to consider Payton's post-crime religious conversion.

Though the Ninth Circuit Court of Appeals, in Payton v. Woodford (258 F.3d 905 [2001]), granted the petitioner relief, the U.S. Supreme Court reversed that ruling. The justices did not find a "reasonable likelihood" that the jury used the K instruction in a way that prevented "...the consideration of constitutionally relevant evidence..." despite the prosecuting attorney's unsupported distinction between pre-crime and post-crime mitigating evidence and the failure of the trial court to give the jury an instruction correcting the prosecutor's misstatement of the law.

The decision

Although Justice Breyer concurred with the majority's holding, he did so only because the California courts had not reached "unreasonable conclusions" in interpreting Supreme Court precedent. Stephen Breyer went so far as to say that, had he been a California judge, he would have found the instruction together with the prosecution's closing arguments a violation of the Eight Amendment because he would have found a reasonable likelihood that the combination would have prevented the jury from considering the defendant's post-crime behavior as a mitigating circumstance. Justice Breyer raises an interesting and important empirical issue, which boils down to the problem of how penalty-phase jurors use post-crime behavior when reaching sentencing decisions.

As Justice Souter pointed out in his dissent, "It was settled law that a capital defendant has a plenary right to present evidence going to any aspect of his character, background, or record, as well as to any circumstance particular to the offense, that might justify a sentence less than death, including evidence of the defendant's behavior after the offense."

If post-crime behavior influences the jury decisions, it probably does so as something other than a factor that extenuates the gravity of the crime. As Souter pointed out, actions occurring after the crime cannot logically influence the seriousness of the event. Instead, post-crime behaviors, whether they demonstrate remorse on the part of the defendant or the adoption of a new morality because of religious conversion, argue against the death penalty-through a rehabilitative logic.

Empirical investigations of post-crime mitigation on juror sentencing–compared with the effects of mitigating conduct before or at the same time as the crime–could add considerably to the analysis of penalty-phase sentencing. Other important factors researchers can examine are the language in the catchall instructions and any admonishments or clarifying comments that the trial judge offers (or could have offered) to supplement the approved penalty-phase instructions.

An empirical analysis of sentencing behavior under these conditions should be of interest to psychologists, as well as legal scholars struggling to understand the requirements of the Eighth Amendment in capital murder trials.