Amid fears of another botched execution, Alabama plans to put James Barber to death on Thursday or early Friday after a federal appeals court upheld a decision not to halt his execution despite his claim that lethal injection could result in cruel and unusual punishment.

Barber, sentenced to death for the 2001 murder of 75-year-old Dorothy Epps, is scheduled to be executed at any time during a 30-hour period that began at midnight Thursday morning and will last until 6 a.m. Friday, court documents show.

The inmate sought to have a US District Court prevent the state from executing him by any method other than nitrogen hypoxia, an alternative to lethal injection that is allowed under Alabama law but has yet to be used.

Barber argued an execution by lethal injection would violate his rights under the Eighth Amendment, according to his initial complaint, which pointed to three allegedly botched executions in Alabama last year, in which Barber's attorneys said Department of Corrections officials struggled to set intravenous lines in the condemned inmates' veins to deliver the fatal drugs.

One of those executions ultimately resulted in the death of the inmate while the two others were called off, with the state citing time constraints due to late-night court battles that prevented the executions from being carried out before the inmates' execution warrants expired. Taken together, they prompted heightened scrutiny of Alabama's lethal injection process and led Gov. Kay Ivey last November to ask Attorney General Steve Marshall to halt executions for a "top-to-bottom review" of its protocol.

In February, Ivey said executions could resume after the Department of Corrections completed its review and said it would take several steps to address issues with the lethal injection protocol, including expanding the pool of personnel available for the execution team and conducting rehearsals to ensure staff were well-trained, among other steps.

But Barber -- who would be the first inmate executed since the review -- argued Alabama had "not made any meaningful improvements to their lethal injection protocol," according to his motion for a preliminary injunction, other than by expanding the window in which officials could carry out an execution.

In his appeal, Barber's attorneys argued he faces a "substantial risk of severe harm" due to his elevated body mass index, which they said makes it more difficult to access his veins. This complication makes him vulnerable to suffering a failed lethal injection, they said.

Instead, Barber had asked to be put to death by nitrogen gas. The state legislature has approved this alternative execution method, but the state has said it hasn't finalized its protocols.

The US District Court for the Middle District of Alabama denied Barber's motion, prompting his attorneys to appeal earlier this week to the 11th Circuit. That court, however, similarly rejected Barber's argument by upholding the district court's decision in an opinion Wednesday. The judges wrote, in part, that the inmate's claim he would suffer the same problems as the inmates before him was "purely speculative" in light of the Department of Corrections' newly-implemented changes.