TALLAHASSEE, Fla. (AP) — The Florida Supreme Court said Thursday it erred in 2016 when it ruled a jury must be unanimous in deciding a convicted murderer should be sentenced to death, announcing a dramatic legal reversal that could affect dozens of death row cases.

The opinion pulled back from the court's 2016 state Supreme Court decision that subsequently led the Legislature to change Florida law to fit the ruling. It remained unclear how the court's turnabout would effect that existing law.

Since the 2016 ruling, dozens of death row inmates who were sentenced to die on non-unanimous jury decisions have been granted new sentencing hearings.

Thursday's ruling involved a 2005 conviction for a slaying in Polk County. A trial judge granted inmate Mark Poole a new sentencing hearing, but the state appealed.

The Supreme Court agreed with the state in that case and said Poole's death sentence should stand in the case of a man killed in 2001 while trying to defend a pregnant woman being attacked by Poole.

“It is no small matter for one Court to conclude that a predecessor Court has clearly erred,” the court said in its ruling. “Our court ... got it wrong.”

"Even though some of these cases are from many years ago, my office remains committed to obtaining justice and closure for the victims and their families. The Supreme Court’s ruling in the Poole case brings us closer to that reality," said State Attorney Brian Haas in a statement to ABC Action News.

Julius Chen, the lawyer who represented Poole in arguments before the state Supreme Court, said in an emailed statement that the decision was “nothing short of astonishing.”

“We are carefully exploring avenues for further review in Mr. Poole's case,” Chen added without elaborating.

Meanwhile, the Legislature is wrapping up the second week of an annual 60-day session and it was too early to tell whether lawmakers had the political will to again change the death penalty law in light of Thursday's ruling. And the exact repercussions of the decision on an array of cases remained unclear.

The state attorney general's office said it was reviewing the ruling.

Senate President Bill Galvano's office said he is also reviewing the ruling.

“This week’s court decision on the death penalty, while reversing a prior decision, does not impact the 2017 statute we passed that requires unanimity of the jury for a death sentence. That statute remains on the books because the law can require more than the Constitutional floor," said Florida House Speaker Jose Oliva in a statement to ABC Action News.

But Thursday's opinion caused an immediate outcry among inmate advocates. They called the decision a retreat on a critical element for ensuring justice in cases in which the death penalty is being sought.

Shalini Goel Agarwal, managing attorney for the Southern Poverty Law Center, said unanimity must rule in any death penalty decisions since “there is no do-over after an execution."

“Given the abundant evidence of wrongful convictions and racial disparities in death sentences, requiring a unanimous jury is fundamental to ensure fairness when exacting the ultimately penalty,” Agarwal said in a statement.

Floridians for Alternatives to the Death Penalty called the decision disappointing.

"To lower the standards and lower the bar on what’s required to send someone to death row we should be raising the standards. And even with the higher standards in place to require a unanimous jury in 2019 Florida led the nation in the number of new death sentences so there’s no reason to change it and make it easier," said the organization's executive director, Mark Elliott.

There was one harsh dissenting opinion to Thursday's ruling. Justice Jorge Labarga noted Alabama is the only state in the nation that doesn't require a unanimous jury decision to impose the death penalty.

“The majority returns Florida to its status as an absolute outlier among the jurisdictions in this country that utilize the death penalty," Labarga wrote. “The majority gives the green light to return to a practice that is not only inconsistent with laws of all but one of the twenty-nine states that retain the death penalty, but inconsistent with the law governing the federal death penalty.”

Criminal trial attorney Bjørn Brunvand said he agreed with the statement.

"The ruling by the Florida Supreme Court in Poole, is a sad and troubling retreat to a similar death penalty scheme to our former unconstitutional system of death penalty injustice," Brunvand stated in part. "I worry about the uncertainty awaiting those who have already had their death sentences vacated for a new sentencing hearing based on Hurst."

The composition of the Florida high court has gone from leaning liberal in 2016 to firmly conservative. Three liberal justices on the seven-member court were forced to retire because of age limits on the same day Republican Gov. Ron DeSantis took office. That gave DeSantis the opportunity to appoint three conservative judges. Two of those justices have since been appointed to a federal appeals court and were not part of Thursday's 4-1 decision.

Confusion over Florida's death penalty laws began after a 2016 U.S. Supreme Court ruling in the case of Timothy Lee Hurst, who was convicted of using a box cutter to kill a coworker at a Pensacola fast-food restaurant in 1998. A judge imposed the death sentence after a 7-5 jury recommendation.

The U.S. Supreme Court ruled the sentence was unconstitutional because the judge had too much weight in the decision.

Executions were halted for months while the state sorted out the issue. The Legislature first passed a bill requiring a 10-2 jury recommendation, but the state Supreme Court overturned it. In 2017, the law was changed to require a unanimous jury decision.

As dozens of death penalty cases were returned to trial court for new sentences, some prosecutors opted to simply agree to sentences of life without parole to avoid new sentencing hearings, often to spare families the pain of reliving their tragedies.

"For those who have already had their resentencing hearing it has no affect whatsoever. For those that are pending resentencing hearings it means that they’ll just review what the verdict was in the number of jurors who voted for death and if the judge overruled that does it comport with this Poole case decision," said ABC Action News legal analyst and WMU-Cooley Law School professor Jeffrey Swartz.

Right now 340 people are sitting on death row, according to the Florida Department of Corrections. That includes cases from Hillsborough County.

"When the decision came out yesterday from the Supreme Court we realized that this was opening the door to the legislature rolling back the unanimity requirement. Our hope is that the legislature doesn’t walk through that door because we feel like that would be a step backwards for Florida," said State Attorney Andrew Warren.

Warren said there is no immediate to his office, covering Hillsborough County.

"It impacts a couple cases where there had been a death penalty, a death sentence, where the verdict was not unanimous. Those cases had come back to our office and there were a couple cases where we were continuing to seek the death penalty, now it’s going to be a question of whether we need to based on what the jury’s verdict was," he said.

