The Supreme Court, in a crushing defeat for opponents of capital punishment, ruled yesterday that state death penalty laws are constitutional even when statistics indicate they have been applied in racially biased ways.

The justices upheld Georgia's death penalty law by a 5-4 vote.

They said statistics showing that killers of white victims are given death sentences far more frequently than killers of Black victims do not establish that the Georgia system violates the Constitution's equal-protection guarantees.

The closely watched Georgia dispute, perhaps the most important capital punishment case in a decade, had been hailed as the last sweeping attack against the death penalty.

Death penalty opponents fell one vote short of casting into doubt the fates of many of the nearly 1900 men and women on death rows nationwide.

Writing for the court's majority, Justice Lewis F. Powell said the statistical study of Georgia's death penalty system "at most indicates a discrepancy that appears to correlate with race."

Powell added, "Apparent disparities in sentencing are an inevitable part of our criminal justice system.... Where the discretion that is fundamental to our criminal process is involved, we decline to assume that what is unexplained is invidious."

The ruling upheld the death sentence given to Warren McCleskey for the 1978 murder of an Atlanta policeman.

"It [the decision] institutionalizes racism and reaffirms the reality that the punishment for killing a white person is far greater then the punishment for killing a Black person," said Professor of Law Alan M. Dershowitz.

"It's a throw back to Jim Crow laws," he said. "It shows that the Supreme Court is leading the lynch mob."

McCleskey's hopes to avoid death in the state's electric chair had been pinned on a study by a University of Iowa law professor, David Baldus.

In his study, Baldus examined every Georgia murder conviction from 1973 to 1978 and found that those who killed whites were 11 times more likely to receive the death penalty than were those who killed Blacks.

Looking at the smaller number of cases in which the greatest jury discretion was exercised in sentencing, Baldus found that killers of whites were four times more likely to receive death sentences.

"The Baldus study does not demonstrate a constitutionally significant risk of racial bias affecting the Georgia capital-sentencing process," Powell wrote yesterday.

"The Constitution does not require that a state eliminate any demonstrable disparity that correlates with a potentially irrelevant factor in order to operate a criminal justice system that includes capital punishment," Powell said.

He said it is state legislatures, not the courts, which must evaluate such statistical studies and determine "the appropiate punishment for particular crimes."

Chief Justice William H. Rehnquist and Justices Byron R. White, Sandra Day O'Connor and Antonin Scalia joined Powell's opinion.

Justices William J. Brennan, Thurgood Marshall, Harry A. Blackmun and John Paul Stevens dissented.

"Narrowing the class of death-eligible defendants is not too high a price to pay for a death penalty system that does not discriminate on the basis of race," Brennan wrote for the four dissenters.

Nationwide, about 95 percent of death row inmates killed whites even though blacks are more often the victims of murder in this country.