Brian Keith Terrell is scheduled to be executed tonight for a 1992 Coweta County murder he says he did not do — the beating death of a 70-year-old friend of his mother’s.

On Monday, as expected, his lawyers went to the State Board of Pardons and Paroles and to the courts with pleas for mercy. Their claims ranged from questioning the witnesses who testified against him to revisiting the issue of potential problems with the compounded drug made specifically to put him to death.

"My son is innocent and I'm asking the Parole Board … to let him come home for time served," Barbara Terrell said after she met with the board for about three hours Monday along with friends, other relatives and her son's lawyers.

In the afternoon the board heard from Newton County District Attorney Layla Zon and Alan Cook, who prosecuted Terrell.

Terrell, 47, was convicted of beating John Watson to death just a few days after the older man discovered Terrell had written checks on his bank account totalling $8,700.

Terrell’s mother found Watson’s body when she went to his house after the local dialysis clinic told her the Covington man had missed his appointment that morning.

“He was my friend,” Barbara Terrell said in an interview with The Atlanta Journal-Constitution. “I was his caretaker and he was my patient.”

But her son did not kill Watson, she said, and there is new evidence to prove that.

“He just knows the Lord will bring him through this,” Barbara Terrell said. “I can’t see the justice system going through with this thing.”

Much of the testimony against Terrell came from his cousin, Jermaine Johnson. Johnson testified that he drove Terrell to Watson’s house and picked him up. He said Terrell told him he had killed Watson.

Now, however, Terrell’s lawyers say Johnson says he lied because police threatened to charge him with Watson’s murder if he did not help them build a case against his cousin. But the lawyers also wrote that Johnson refuses to sign an affidavit saying under oath that he lied.

Defense lawyers also said a neighbor who testified that she saw Terrell looking under the hood of a car parked at Watson’s house was mistaken.

In court filings, Terrell's lawyers focus on questions about the compounded drug, pentobarbital, made for his execution.

The state had planned to kill Terrell on March 10. But the execution was postponed after the pentobarbital looked cloudy during preparations to execute Kelly Gissendaner, the lone female inmate on Georgia’s death row, on March 2. Gissendaner’s death also was put on hold, but she was eventually executed on Sept. 30.

Terrell’s lawyers wrote in a federal court filing that the state’s records show the pharmacist who will make Terrell’s pentobarbital has a 50 percent error rate. “As to alternatives, it would be reasonable to obtain drugs from a compounding pharmacist who does not have such a history of mixing defective drugs,” they wrote.

If Terrell is put to death, he will be the fifth person Georgia has executed this year, more than any other year since Georgia began using lethal injection in 2001.