Tennessee will stop all executions until the end of 2022 pending an independent review of procedures used by the state to carry out lethal injections, which opponents say can cause undue suffering to those put to death, Governor Bill Lee said on Monday.

The decision for postponing executions was a response to concerns raised by advocates for prisoners on death row over a failure of the state to follow its own procedures for testing the potency and sterility of the drugs.

In the face of those concerns, the state, by order of the governor, delayed the April execution of Oscar Franklin Smith, 72, who was convicted in the 1989 stabbing of his estranged wife and her two children.

In announcing the pause, Lee stressed that he still believed that the death penalty was the appropriate punishment for certain heinous crimes.

Even so, the Republican governor said in a statement, "the death penalty is an extremely serious matter, and I expect the Tennessee Department of Correction to leave no question that procedures are correctly followed."

Kelley Henry, the chief death row defense attorney with Federal Public Defender's office in Nashville filed the complaint that spurred Lee to grant the temporary reprieve for all death row inmates.

"We feel the governor has shown strong leadership and has taken a step toward accountability," she said.

"The use of the three-drug cocktail is incredibly problematic and in other states has caused spectacular failures," Henry said, referring to the apparently painful deaths of some inmates after lethal injections. "Our clients would suffer inhumane deaths," she said.

Former U.S. Attorney Ed Stanton will oversee the independent review for Tennessee, the governor's release said.

"We will pause scheduled executions through the end of 2022 in order to allow for the review and corrective action to be put in place," Lee said in a statement.

Smith was one of five death row inmates scheduled to be executed this year in Tennessee. At present 46 men and one woman are on the state's death row, according to the Department of Correction. The last execution carried out in the state was in February 2020.