NASHVILLE (AP) — After an undisclosed "oversight" forced Tennessee to call off the execution of Oscar Smith an hour before he was to die last week, Smith's attorneys on Thursday asked for a moratorium on executions and a review of the state's execution protocols.

Federal Public Defender Kelley Henry, speaking at a Thursday news conference, said there needs to be an independent investigation of what went wrong. The state's reluctance to promptly disclose what happened undermines public confidence in their ability to carry out an impartial investigation, she said.

Gov. Bill Lee issued a brief statement on April 21 at 5:42 p.m. saying that "due to an oversight in preparation for lethal injection, the scheduled execution of Oscar Smith will not move forward tonight. I am granting a temporary reprieve while we address Tennessee Department of Correction protocol."

Officials initially said Lee would release more details this week but have since postponed any disclosures until next Monday. Lee spokesperson Laine Arnold explained in an email that they were delaying the information's release so as not to distract from the end of the General Assembly's legislative session this week.

Henry declared herself "baffled" about the delay. "I don't see how the two are connected," she said.

While Smith and his attorneys do not yet know what prompted the execution's abrupt halt, Henry said that the night before the execution she requested the results of tests for "potency, sterility and endotoxins" that are supposed to be carried out on the execution drugs if they are obtained from a compounding pharmacy. She has not received a response.

Henry suspects at least two of the three execution drugs were compounded, rather than commercially manufactured, she said, although secrecy rules surrounding Tennessee executions makes it difficult to know for certain.

After a public outcry several years ago, many drug manufacturers began refusing to sell their medications for executions, making the drugs difficult for prison systems to obtain. Around the same time, Tennessee and many other states began approving exemptions to open records law that allows the names of drug suppliers and other information about executions to remain secret.

Through a public records request, Henry said she has received heavily redacted records from the state's last lethal injection execution in 2019 and believes the drugs in that case did not pass the required tests.

Asked whether the governor had a response to the petition for a moratorium, Arnold said in an email that Lee will have more to say about it on Monday.

Smith was convicted of fatally stabbing and shooting his estranged wife, Judith Smith, and her teenage sons, Jason and Chad Burnett, at their Nashville home on Oct. 1, 1989. At 72, Smith is the oldest inmate on Tennessee's death row. His reprieve expires on June 1, after which the state Supreme Court will set a new execution date.