A lawyer for condemned murderer Brian Keith Terrell is again raising questions about the compounded lethal injection drug that Georgia uses in executions.

Terrell is scheduled to die on Tuesday. He was originally slated for execution on March 10, one week after the scheduled execution of female death row inmate Kelly Gissendaner.

Both of those executions were put on hold temporarily when the compounded lethal injection drug, pentobarbital, turned cloudy. But Gissendaner was eventually executed in September after the state decided the drug's cloudiness was caused by how it was stored, not how it was made.

Now, in an appeal filed Thursday in Fulton County Superior Court, Terrell's attorney argues the Georgia Department of Corrections never truly discovered what caused the problem, so the agency continues to insist cold temperatures caused clumps to form in the pentobarbital.

Terrell’s lawyer, Bo King, wrote in the appeal that information obtained under the Georgia Open Records Act indicate there were problems with two batches of pentobarbital, not just one, suggesting the cloudiness might not be an isolated incident.

“It is only a matter of time before the drugs — compounded by an unknown pharmacy using unknown ingredients in unknown circumstances — become defective again,” King wrote.

The attorney also wrote that the defense team's expert on compounding drugs reviewed state records but was limited by Georgia's secrecy law. The drug expert, Michael Jay, decided other circumstances could have caused the problem with the pentobarbital.

Jay, a professor of pharmaceutical sciences and bio-medical engineering at the University of North Carolina-Chapel Hill, wrote in a document attached to Terrell’s appeal that if officials had not noticed a problem with the drug and had used it as intended in March, Gissendaner — and later Terrell — would have suffered excruciating pain.

Jay wrote that he suspects the compounding pharmacist who made those batches of drugs used the wrong active ingredient — pentobarbital rather than pentobarbital sodium. Either that, or the pH solution in the compounded drug was incorrect.

If those executions had been carried out using the drugs, Jay wrote, it’s possible that particulate matter in the pentobarbital would have lodged in blood vessels or the lungs. It would be akin to being injected with “very small pieces of glass,” Jay wrote.

The sources of Georgia's lethal injection drug, and the state secrecy shrouding that information, is an issue that has been raised several times in appeals. Repeatedly the courts have upheld the use of pentobarbital and have ruled that Georgia can keep secret its drug sources to protect pharmacists from public pressure.

Terrell is scheduled to be executed at 7 p.m. Tuesday for the 1992 murder of John Watson, his mother's friend. Terrell stole about $8,700 from the 70-year-old man by stealing blank checks. Watson told Terrell's mother he wouldn't press charges if Terrell returned most of the money. Two days later, Terrell attacked Watson as he left his Newton County house for a dialysis appointment.

Fulton Superior Court Judge Ural Glanville will hold a hearing Monday on Terrell's latest appeal. At the same time, the state Board of Pardons and Paroles will hear his petition for clemency.