A man on death row in Mississippi for the 1976 murder of a Metairie-raised woman should not be executed until it is determined whether the state’s lethal-injection drug combination is constitutional, a federal judge in Mississippi decided Tuesday.

The ruling by U.S. District Judge Henry Wingate, of Jackson, came almost a month after the Attorney General’s Office in Mississippi asked the state Supreme Court to set an execution date no later than Thursday for death row inmate Richard Gerald Jordan, 69.

Although the Supreme Court has not responded to that request, Wingate is presiding over a federal lawsuit filed by Jordan and another death-row inmate alleging that the combination of drugs Mississippi has been using in lethal injections could cause them great pain before killing them, violating the constitutional mandate against cruel and unusual punishment.

Jordan’s attorneys at the MacArthur Justice Center in New Orleans had asked Wingate to issue a preliminary injunction preventing the setting of an execution date until he rules on the lawsuit. Wingate granted that request Tuesday, meaning that Jordan — Mississippi’s longest-serving death row inmate — will remain there even longer unless the judge’s ruling is overturned.

Jordan was convicted of fatally shooting 34-year-old Edwina Marter shortly after kidnapping her for $50,000 ransom in Gulfport, Mississippi, on Jan. 12, 1976. Jordan targeted Marter — a mother of two who attended East Jefferson High School and St. Catherine of Siena School in Metairie while growing up — after learning her husband was a vice president at a Gulfport bank.

Jordan claimed he accidentally killed Marter while trying to stop her from fleeing. But evidence demonstrated that she was kneeling in front of Jordan when he shot her in the back of the head in northern Harrison County, Mississippi, prosecutors said.

Jordan was found guilty of Marter’s killing and sentenced to death that same year. He subsequently won three appeals for various reasons but was resentenced to death each time. He has now exhausted his appeals but in April filed the lawsuit pending in front of Wingate.

The suit questions whether Mississippi could safely mix an effective form of the anesthetic pentobarbital, the first of three drugs used in the state’s lethal injections.

Jordan’s lawyers claimed there were problems with using pentobarbital — considered an “intermediate-acting” barbiturate — in Mississippi. They said Mississippi’s own laws require what’s known as an “ultra short-acting” barbiturate to be used in lethal injections.

On July 28, Mississippi’s Department of Corrections notified Wingate that it was amending its lethal-injection protocol to use the anesthetic midazolam as the first drug, which the U.S. Supreme Court recently found to be constitutional. The Mississippi Attorney General’s Office almost simultaneously asked the state’s high court to set an execution date for Jordan within 30 days.

But employing midazolam for lethal injections in Mississippi is as problematic as using pentobarbital, according to Jordan’s legal team, led by the co-director of New Orleans’ MacArthur Justice Center, Jim Craig. He said midazolam is not even a barbiturate.

Marter’s surviving relatives said Jordan should have been executed many years ago.

“It breaks all of our hearts, all these years, that (Jordan) hasn’t left the picture,” Marter’s sister, Norma de Gruy Wells, 73, of Metairie, said recently. “He’s in the picture. But she isn’t. He took her out.”