WASHINGTON — (AP) — The Justice Department is rescinding its protocol for federal executions that allowed for single-drug lethal injections with pentobarbital, after a government review raised concerns about the potential for "unnecessary pain and suffering."

Attorney General Merrick Garland's order to withdraw the lethal injection policy comes days before President-elect Donald Trump, who is expected to restart federal executions, is set to return to the White House. Trump's Justice Department could reinstate the protocol to use pentobarbital as a single drug to carry out executions.

A moratorium on federal executions has been in place since 2021, and only three defendants remain on federal death row after Democratic President Joe Biden converted 37 of their sentences to life in prison.

The governments’ findings about the potential risks of unnecessary pain could have broader implications. Legal challenges have been brought in several states where pentobarbital is the primary method of execution, potentially leading to reviews of execution protocols nationwide.

The department's review of scientific and medical research found there remains “significant uncertainty about whether the use of pentobarbital as a single drug lethal injection causes unnecessary pain and suffering," according to a report published Wednesday.

“In the face of such uncertainty, the Department should err on the side of treating individuals humanely and avoiding unnecessary pain and suffering,” Garland wrote in his memo ordering the director of the Bureau of Prisons to rescind the protocol. Garland said it should not be reinstated ”unless and until that uncertainty is resolved."

The report from the Justice Department's Office of Legal Policy noted that the Food and Drug Administration "has not reviewed or approved of the use of pentobarbital in high doses or for the purpose of causing death.”

The pentobarbital protocol was adopted by Bill Barr, attorney general during Trump's first term, to replace a three-drug mix used in the 2000s, the last time federal executions were carried out before Trump was in office. The Trump administration carried out 13 federal executions, more than under any president in modern history.

Under Trump, the Justice Department also sanitized the accounts of the executions carried out in 2020 and 2021. Government lawyers said the process of dying by lethal injection was like falling asleep and they called gurneys "beds" and final breaths "snores." But accounts by reporters from The Associated Press and other media witnesses described how prisoners' stomachs rolled, shook and shuddered as the pentobarbital took effect during executions at the U.S. penitentiary in Terre Haute, Indiana. The AP witnessed every federal execution.

Questions about whether inmates' midsections trembled, as media witnesses reported, were a focus of litigation throughout the series of executions. Inmates' lawyers argued it proved pentobarbital caused flash pulmonary edema, in which fluid rushes through quickly disintegrating membranes into lungs and airways, causing pain akin to being suffocated or drowned. The Constitution prohibits execution methods that are "cruel and unusual."

Several states also have policies allowing single-drug executions with pentobarbital. Tennessee announced last month that it would use the single drug to carry out executions that have been halted since 2022. The state's previous protocol called for three different drugs to be used in a series.

Shawn Nolan, a lawyer who has represented federal death row inmates, said in a statement that the report makes clear that “no jurisdiction, federal or state, should continue using this cruel, unconstitutional execution method.”

The chief of the federal public defender’s habeas unit in Nashville, Tennessee, Kelley Henry, said the review was “a damning condemnation of the use of pentobarbital to poison prisoners to death” and that Tennessee "should rescind its execution protocol immediately.”

Biden's decision commute the sentences of most death row inmates spared the lives of people convicted in killings, including those of police and military officers, people on federal land and those involved in deadly bank robberies or drug deals, as well as the killings of guards or prisoners in federal facilities.

The decision leaves three federal inmates to face execution. They are Dylann Roof, who carried out the 2015 racist slayings of nine Black members of Mother Emanuel AME Church in Charleston, South Carolina; 2013 Boston Marathon bomber Dzhokhar Tsarnaev; and Robert Bowers, who fatally shot 11 congregants at Pittsburgh's Tree of life Synagogue in 2018, the deadliest antisemitic attack in U.S history.

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Associated Press writer Travis Loller in Nashville, Tennessee, contributed to this report.

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