At the risk of -- no, for the purpose of -- inflaming the body politic, I herewith call attention to the Supreme Court's sudden discovery of yet another constitutional right. It is the right of a convicted criminal in a capital case to prevent a jury, as it considers his sentence, from receiving reports or testimony about the suffering spread by his crime.

In a case concerning a double murder, the court ruled 5-4 that the prohibition of ''cruel and unusual punishments'' is violated if a state presents jurors with evidence of the impact of a murder on the victim's family.

In 1983 in West Baltimore, an elderly couple were murdered by John Booth and a friend. The victims were stabbed with a kitchen knife.

Maryland requires a pre-sentence report that includes a ''victim-impact statement'' assessing the effect of crimes on others. In this case, the statement documented the sort of radiating suffering that killings often cause. Relatives suffered from sleeplessness, unfocused fear, panic when a loved one was late arriving home. The killings were for the relatives ''a completely devastating and life-altering experience.''

The court ruled that in capital cases such information is ''irrelevant.'' Justice Powell (joined by Brennan, Marshall, Blackmun and Stevens) said that an impact statement ''can serve no other purpose than to inflame the jury,'' is ''inconsistent with reasoned decision-making'' and poses a risk that death sentences will be imposed ''arbitrarily.''

The majority's rickety argument rests on a preposterous principle: that a criminal's ''personal responsibility and moral guilt,'' his blameworthiness, is unrelated to the suffering his crime causes. The court says that because death is a sentence unlike any other, it is impermissible to permit impact statements that might intrude ''arbitrariness'' into sentencing in capital cases.

Justice Scalia, joined in dissent by Rehnquist, White and O'Connor, notes that a defendant's eligibility for the death sentence often turns upon conditions that are independent of his moral guilt, when that is understood only in terms of intentions. If a bank robber aims at a guard, shoots and kills, the robber can be executed. If the gun misfires, he cannot.

Scalia notes that a driver will lose his license for reckless driving if he drives 60 m.p.h. in a residential neighborhood. If his recklessness results in a death, he will go to jail for manslaughter. His ''personal responsibility,'' measured by his inner life -- his intentions -- is identical in both cases. But as the consequences differ, so does the appropriate punishment. As White says, the court would not overturn a sentence for reckless homicide by automobile merely because the punishment exceeded the maximum punishment for reckless driving.

The majority is troubled by the fact that some relatives of murder victims will be more articulate, passionate and moving than others, so not all murderers will be equally jeopardized by victim-impact statements. Therefore such statements impart ''arbitrariness'' in sentencing. For the majority, ''arbitrary'' describes any deviation from perfect equality of risk for defendants. But as White says, a criminal-justice system purged of such ''arbitrariness'' is a chimera. No two prosecutors are of equal ability, no two witnesses are of equal impact on juries.

The court has hitherto held that sentencing considerations are ''peculiarly questions of legislative policy'' because ''in a democratic society legislatures, not courts, are constituted to respond to the will and consequently the moral values of the people.'' However, the court's fine-tuning of sentencing procedures in capital cases has resulted in an entitlement: defendants are entitled to introduce mitigating evidence. Yet now the court has held that a state cannot counter that with evidence concerning the consequences of the crime. As Scalia says, debates about sentencing must now proceed with one side muted.

Punishment may serve several purposes. It may reform the person punished. It may deter others from following his path. But all punishment necessarily is expressive. It expresses community values. The court, by trying to prevent juries in capital cases from being ''inflamed,'' is trying to prevent the expression of outrage, even outrage about -- no, especially outrage about -- the most outrageous of crimes.

But surely there is a distinction to be drawn between passion that unhinges reason and passion that is a reasonable (that is, proportionate and just) response to facts (such as the consequences of crimes).

The court ruled the day before a New York jury acquitted Bernhard Goetz of attempted murder. Goetz exemplifed one way that anger can be vented. A better way is through a jury that has been properly, reasonably, inflamed by narrowing truths contained in a victim-impact statement.