WASHINGTON — Black lives do not matter nearly as much as white ones when it comes to the death penalty, a new study has found. Building on data at the heart of a landmark 1987 Supreme Court decision, the study concluded that defendants convicted of killing white victims were executed at a rate 17 times greater than those convicted of killing Black victims.

There is little chance that the new findings would alter the current Supreme Court’s support for the death penalty. Its conservative majority has expressed impatience with efforts to block executions, and last month it issued a pair of 5-4 rulings in the middle of the night that allowed federal executions to resume after a 17-year hiatus.

But the court came within one vote of addressing racial bias in the administration of the death penalty in the 1987 decision, McCleskey v. Kemp. By a 5-4 vote, the court ruled that even solid statistical evidence of race discrimination in the capital justice system did not offend the Constitution.

The decision has not aged well.

In 1991, after he retired, Justice Lewis F. Powell Jr., the author of the majority opinion, was asked whether there was any vote he would like to change.

“Yes,” he told his biographer. “McCleskey v. Kemp.”

One of the dissenters in the case, Justice John Paul Stevens, was still stewing over it after his own retirement in 2010.

“That the murder of Black victims is treated as less culpable than the murder of white victims provides a haunting reminder of once-prevalent Southern lynchings,” he wrote that year in The New York Review of Books.

Opponents of the death penalty have been deeply critical of the decision, comparing it to the Dred Scott case, the Supreme Court’s 1857 ruling that enslaved Black people were property and not citizens.

“McCleskey is the Dred Scott decision of our time,” Anthony G. Amsterdam, a law professor at New York University, said in a 2007 speech. “It is a declaration that African American life has no value which white men are bound to respect. It is a decision for which our children’s children will reproach our generation and abhor the legal legacy we leave them.”

The McCleskey decision considered a study conducted by David C. Baldus, a law professor who died in 2011. It looked at death sentences rather than executions, and it made two basic points.

The first was that the race of the defendant does not predict the likelihood of a death sentence. The second was that the race of the victim does.

Killers of white people were more than four times as likely to be sentenced to death as killers of Black people, Baldus found.

The new study, published in The Harvard Civil Rights-Civil Liberties Law Review, examined not only death sentences but also whether defendants sentenced to death were eventually executed. “The problematic sentencing disparity discovered by Baldus is exacerbated at the execution stage,” wrote the study’s authors, Scott Phillips and Justin Marceau of the University of Denver.

Baldus’ study examined more than 2,000 murders in Georgia from 1973 to 1979, controlling for some 230 variables.

Though some have argued that Baldus did not consider every possible variable, few question his bottom-line conclusion, and other studies have confirmed it.

In 1990, the General Accounting Office, now called the Government Accountability Office, reviewed 28 studies and determined that 23 of them found that the race of the victim influenced “the likelihood of being charged with capital murder or receiving a death sentence.”

“This finding was remarkably consistent across data sets, states, data collection methods and analytic techniques,” the report said. A 2014 update came to a similar conclusion.

One factor Baldus could not analyze, given the decades that often pass between sentencings and executions, was whether the race of the victim correlated to the likelihood of the defendant being put to death.

The new study, the product of exhaustive research, supplied the missing information. It found that 22 of the 972 defendants convicted of killing a white victim were executed, compared with two of the 1,503 defendants convicted of killing a Black victim.

The new study also confirmed just how rare executions are. Of the 127 men sentenced to death in the Baldus study, 95 left death row thanks to judicial action or executive clemency; five died of natural causes; one was executed in another state; one escaped (and was soon beaten to death in a bar fight); and one remains on death row.

A more general and less granular 2017 study compared two sets of nationwide data: homicides from 1975 to 2005 and executions from 1976 to 2015. Its conclusions were similarly striking.

About half of the victims were white, that study found, but three-quarters of defendants put to death had killed a white person. About 46% of the victims were Black, but only 15% of defendants who were executed had killed a Black person.

Eric M. Freedman, a law professor at Hofstra, said courts and lawmakers had failed to confront the question of racial bias in the administration of capital punishment.

“The continuing adherence of the Supreme Court to McCleskey is a continuing statement that Black lives do not matter,” he said. “The continuing failure of Congress and the state legislatures to remedy the situation is a continuing admission that the states are unable to run racially unbiased death penalty systems.”

Phillips, one of the authors of the new study, said the issue was part of a broader societal struggle.

“It’s not necessarily that the death penalty has a race problem,” he said. “It’s more that the United States has a race problem that happens to infect the death penalty.”