<p>The Supreme Court struck down the death penalty altogether in 1972 due to the <a href="https://www.thoughtco.com/death-penalty-in-the-united-states-721138" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="1">arbitrary enforcement</a> of death penalty laws. As one might expect from a state in the Deep South in the mid-twentieth century, Georgia&#39;s arbitrary enforcement tended to correlate along racial lines. Justice Potter Stewart, writing for a Supreme Court majority, declared a moratorium on the death penalty in the United States:</p><blockquote>These death sentences are cruel and unusual in the same way that being struck by lightning is cruel and unusual. For, of all the people convicted of rapes and murders in 1967 and 1968, many just as reprehensible as these, the petitioners are among a capriciously selected random handful upon whom the sentence of death has in fact been imposed. My concurring Brothers have demonstrated that, if any basis can be discerned for the selection of these few to be sentenced to die, it is the constitutionally impermissible basis of race … But racial discrimination has not been proved, and I put it to one side. I simply conclude that the Eighth and Fourteenth Amendments cannot tolerate the infliction of a sentence of death under legal systems that permit this unique penalty to be so wantonly and so freakishly imposed.</blockquote>This moratorium would not, however, prove permanent.After Georgia revised its death penalty laws to address arbitrariness, Justice Stewart wrote again for the Court, this time reinstating the death penalty provided that checks and balances are in place to ensure that some objective criteria are used to determine its enforcement:<blockquote>The basic concern of Furman centered on those defendants who were being condemned to death capriciously and arbitrarily. Under the procedures before the Court in that case, sentencing authorities were not directed to give attention to the nature or circumstances of the crime committed or to the character or record of the defendant. Left unguided, juries imposed the death sentence in a way that could only be called freakish. The new Georgia sentencing procedures, by contrast, focus the jury&#39;s attention on the particularized nature of the crime and the particularized characteristics of the individual defendant. While the jury is permitted to consider any aggravating or mitigating circumstances, it must find and identify at least one statutory aggravating factor before it may impose a penalty of death. In this way, the jury&#39;s discretion is channeled. No longer can a jury wantonly and freakishly impose the death sentence; it is always circumscribed by the legislative guidelines. In addition, the review function of the Supreme Court of Georgia affords additional assurance that the concerns that prompted our decision in <i>Furman</i> are not present to any significant degree in the Georgia procedure applied here.</blockquote>The history of Supreme Court death penalty law over the past 40 years has centered on adhering to these basic criteria.Prior to 2002, it was completely legal for states to execute mentally handicapped prisoners on equal terms with prisoners who were not mentally handicapped. From a deterrence point of view, this makes no sense—and Justice John Paul Stevens argued in the Court&#39;s majority opinion that, because the punishment makes no sense, it is a violation of the Eighth Amendment:<blockquote>The theory of deterrence in capital sentencing is predicated upon the notion that the increased severity of the punishment will inhibit criminal actors from carrying out murderous conduct. Yet it is the same cognitive and behavioral impairments that make these defendants less morally culpable—for example, the diminished ability to understand and process information, to learn from experience, to engage in logical reasoning, or to control impulses—that also make it less likely that they can process the information of the possibility of execution as a penalty and, as a result, control their conduct based upon that information. Nor will exempting the mentally retarded from execution lessen the deterrent effect of the death penalty with respect to offenders who are not mentally retarded. Such individuals are unprotected by the exemption and will continue to face the threat of execution. Thus, executing the mentally retarded will not measurably further the goal of deterrence.</blockquote>This was not an uncontroversial opinion—justices Scalia, Thomas, and Rehnquist dissented on multiple grounds—and, more pertinently, the fact that the opinion leaves states to decide criteria for classifying someone as mentally handicapped weakens the ruling&#39;s effect considerably.<p>One of the most shocking artifacts of U.S. pre-civil rights policy has been the willingness of Southern state governments to execute children. After pointing out that this has limited practical and deterrent effects, Justice Anthony Kennedy outraged many conservatives by citing international law as a relevant precedent:</p><blockquote>Our determination that the death penalty is disproportionate punishment for offenders under 18 finds confirmation in the stark reality that the United States is the only country in the world that continues to give official sanction to the juvenile death penalty … [O]nly seven countries other than the United States have executed juvenile offenders since 1990: Iran, Pakistan, Saudi Arabia, Yemen, Nigeria, the Democratic Republic of Congo, and China. Since then each of these countries has either abolished capital punishment for juveniles or made public disavowal of the practice. In sum, it is fair to say that the United States now stands alone in a world that has turned its face against the juvenile death penalty.</blockquote>As our understanding of civil liberties continues to evolve, it is likely that the death penalty will become <a href="https://www.thoughtco.com/pros-cons-capital-punishment-3367815" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="1">less widely used</a> over time—but for now, there is at least a body of Supreme Court law that can be used to overturn the most egregious examples of state-level capital punishment enforcement.