NASHVILLE, Tenn. (AP) -- Gov. After revealing that Tennessee's lethal injection drugs had not been properly tested, Bill Lee put an end to executions in Tennessee on Monday. Lee had to stop Oscar Smith's execution an hour before his death last month because of this oversight.

Lee initially didn't disclose the reason Smith was executed, other than to state that there was an "oversight in the preparation" of the lethal injection drug. Tennessee's execution protocols require that any compounded drug be independently tested for potency and sterility. Lee stated Monday that Smith's execution drugs were tested for potency, sterility and endotoxins.

Smith's lawyers had demanded a moratorium of executions and an independent review of the issues last week. Federal Public Defender Kelley Henry stated Monday that the Republican governor's decision is a "great example of leadership".

Henry stated that compounded drugs used in lethal injection are a risky practice. "Failing to test for endotoxins in the context of lethal injection is a violation" Henry said. Governor Lee was right to stop executions due to this breach.

Lee appointed Ed Stanton, a former U.S. attorney, to examine the circumstances that led to this failure. Lee stated in a statement that he will also examine the clarity of Tennessee's lethal injection manual, and review Tennessee Department of Correction staffing.

Lee stated, "I have reviewed each death penalty case and I believe it is an appropriate punishment to punish heinous crime." "However, I believe the death penalty to be a serious matter and that the Tennessee Department of Correction will ensure that the procedures are followed correctly."

Lee stated that the pause will continue to be in effect until the end of the calendar year, to allow for review and corrective actions.

After commercial drug producers refused to sell their drugs for executions, many states switched to compounded drugs. This made it difficult for prisons to obtain the drugs.

Frank Romanelli, a professor of pharmacy at University of Kentucky College of Pharmacy explained the difference as follows: "I can either go buy a Hershey’s chocolate bar or I can make it at home. They're trying to make one at their home. To ensure that it is equal, they need to test it.

Romanelli stated that although endotoxins are usually made from bacteria, it could indicate problems in the manufacturing of drugs. However, the endotoxins would likely not pose a problem in an execution setting. Endotoxins are rarely fatal.

Romanelli believes that Tennessee has lifted the guidelines for execution of its testing protocols.

Romanelli stated, "In their defense they are probably thinking, ‘Let’s keep this as clean and as airtight possible.

Lee stated that the problem with the testing was discovered shortly before execution. He also said that checklists were created on the day of execution to ensure that everything was done properly. That process revealed that one step was not being followed." Lee said, "We hope it never happens again." He also stated, "We're going to implement a process to ensure that each step is properly followed from now on."

Henry stated last week that she asked for the results of the tests the night before execution but was not informed. Henry believes that at least two execution drugs were made from compounded drug, and not commercially manufactured. However, it is difficult to be certain due to the secrecy laws surrounding Tennessee executions.

In recent years, Tennessee and other states have passed exemptions from open records laws. This has made it impossible to reveal the identities of drug suppliers or other details about executions.

Henry was able to obtain heavily redacted records of the state's 2019 execution by lethal injection through a public records request. She believes that the drugs used in this case failed to pass the required tests. Drugs should be tested according to the United States Pharmacopeial Convention standards. Henry stated that she believes the drugs were tested using standards from another country. This could be because they were likely sourced from abroad.

Lee stated that he had asked Stanton for a review of the "adherence to testing policy" since 2018 was the last time the state's lethal injection manual has been updated.

Although lethal injection was initially used as an alternative to the electric chair but it has been the subject a constant stream of lawsuits and problems.

Henry stated at a press conference last week that "every time people in my office have raised issues, they've had the to make adjustments -- regardless of whether it's a wrong drug, the wrong strength, or the USP."

Smith was sentenced for stabbing and shooting his estranged spouse, Judith Smith, as well as her teenage sons Jason and Chad Burnett at their Nashville home on October 1, 1989.

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Reynolds reported from Louisville in Kentucky. Jonathan Mattise contributed to this report from Franklin, Tennessee.