Tennessee’s first execution of a woman in 200 years was halted by a court on Wednesday morning an hour before it was set to take place.

The state governor and the supreme court had earlier refused calls for clemency in the case of Christa Pike, who was convicted of murder 30 years ago.

She was set to die by lethal injection at 11am ET on Wednesday but the execution has been halted by a federal appeals court.

In a 2-1 majority, the court said: “The interests of justice and the finality of Pike’s impending execution compel the entry of a short stay of execution in order to properly analyze the parties’ fully briefed arguments and resolve the issues on the merits.”

Stephen Ferrell, Pike’s attorney, said: “The court has stayed this recognizing the serious concerns about Christa’s scheduled execution.”

The office of Jonathan Skrmetti, the state attorney general, issued a statement reacting to the news on Wednesday, saying: “We will continue to advocate for the lawfully imposed sentence as the courts work through this technical issue. It is common in capital cases for the defense to raise last-minute objections following decades of litigation in numerous courts. We are asking the supreme court of the United States to lift the stay.”

The American Civil Liberties Union, which has opposed Pike’s execution, issued a statement on Wednesday, saying: “Hours before Tennessee was set to execute the first woman in the state in more than 200 years today, a federal court temporarily paused Christa Pike’s execution. Tell Governor Lee to respect the court’s decision and call off her execution now.”

The Guardian has reached out to the office of Bill Lee, Tennessee’s Republican governor.

Ahead of Pike’s scheduled execution, Lee declined to intervene, saying on Tuesday: “After deliberate consideration of Christa Gail Pike’s request for clemency and after a thorough review of the case, I am upholding the sentence of the state of Tennessee and do not plan to intervene.”

Pike, who is now 50, was 18 when she and her boyfriend, who was 17 at the time, killed 19-year-old Colleen Slemmer, one of their classmates at Knoxville Job Corps in 1995.

The case garnered nationwide headlines due to the ages of those involved and the brutality of the murder.

According to prosecutors, Pike was worried that Slemmer was trying to take her then boyfriend, Tadaryl Shipp, away fom her. Together, they lured Slemmer into a wooded area behind the agriculture campus steam plant at the University of Tennessee on 12 January 1995. Pike then cut Slemmer’s stomach and throat with a box cutter before smashing her head with a rock.

Shipp carved a pentagram into Slemmer’s chest and Pike later showed a friend a fragment of Slemmer’s skull.

Shipp was convicted of first-degree murder in 1997 and was given a life sentence with the possibility of parole.

Pike has never denied her involvement in Slemmer’s killing and was later diagnosed with bipolar disorder and post-traumatic stress disorder.

“I was a mentally ill 18-year-old kid. It took me numerous years to even realize the gravity of what I’d done. Even more to accept how many lives I affected. I took the life of someone’s child, sister, friend. It sickens me now to think I had the ability to commit such a crime,” Pike said in a statement that was included in her clemency petition.

On Saturday, May Martinez, Slemmer’s mother, said she was waiting for Pike’s execution.

“Every time I think about it, I think about Colleen feeling that pain and trying to get up and run,” Martinez told the Associated Press, adding: “Not a day goes by, or a minute goes by that I do not think about Colleen. Holidays are the worst.”

The Associated Press contributed reporting