An inmate convicted in the mail-bomb death of a federal judge killed during a wave of Southern terror in 1989 was scheduled to be executed Thursday as the oldest prisoner put to death in the United States in modern times. Walter Leroy Moody Jr., 83, is scheduled to receive a lethal injection Thursday evening. At his 1996 trial, prosecutors described Moody as a meticulous coward who committed murder by mail because of his obsession with getting revenge on the legal system, and then committed more package bombings to make it look like the Ku Klux Klan was behind the judge's murder. If his execution is carried out, Moody will be the oldest inmate put to death since executions resumed in the U.S. in the 1970s, according to the non-profit Death Penalty Information Center. His attorneys have not raised his age in legal filings, but have argued in a clemency petition to Alabama's governor that his age and health would complicate the lethal injection procedure. Judge Robert S. Vance, a member of the Atlanta-based 11th U.S. Circuit Court of Appeals, was at his kitchen table in Mountain Brook, Alabama, on Dec. 16, 1989, when he opened a package after a morning of errands and yard work. The explosion ripped through the home near Birmingham, killing Vance instantly and severely injuring his wife, Helen. Prosecutors said Moody, who had attended law school, had a grudge against the legal system because the 11th Circuit refused to overturn a 1972 pipe-bomb possession conviction that prevented him from practicing law. Authorities said Moody mailed out a total of four package bombs in December 1989. A device linked to Moody killed Robert E. Robinson, a black civil rights attorney from Savannah, Georgia. Two other mail bombs were later intercepted and defused, including one at an NAACP office in Jacksonville, Florida. Authorities said those bombs were meant to make investigators think the crimes were racially motivated. Moody was first convicted in 1991 in federal court and sentenced to seven life terms plus 400 years. He was later convicted in state court in 1996 and sentenced to death for Vance's murder. Moody's attorneys asked the U.S. Supreme Court to stay his execution in order to review whether his federal sentence, which was handed down first, can be interrupted. They also argued that the aggravating factors used to impose a death sentence were improper. Separately, Moody's lawyer asked the Alabama Supreme Court to block the lethal injection arguing that an emergency medical technician who assessed Moody on Wednesday told the inmate he had 'spider veins' and seemed concerned. Alabama halted an execution last month after workers couldn't find a usable vein on a 61-year-old inmate. Vance's son, Robert Vance Jr., now a circuit judge in Jefferson County and Democratic candidate for chief justice in Alabama, said it's important that people remember how his father lived, not just how he died. 'He was a great judge, a great lawyer before that, and a great father,' he said. Friends said the senior Vance quietly fought for the rights of underprivileged as both a jurist and a politician. As chairman of the Alabama Democratic Party in the 1960s and early 1970s, Vance worked to bring African-Americans into the party and fought then-Gov. George C. Wallace's and other segregationists effort to control the party machinery, said Al LaPierre, who worked for Vance in the 1970s. 'He believed the Democratic Party should be open and not be the party of George Wallace and the Dixiecrats,' LaPierre said. Moody had sent a letter from death row to the younger Vance claiming he was the innocent victim of a government conspiracy. 'Had my Dad been murdered, I would want to know who had done it,' Moody wrote. Vance said he tossed the letter in the trash. The younger Vance, who does not plan to witness the execution, said he had to make peace with his father's death, but said he has no doubt that Moody is guilty. Moody, he said, fits the definition of a psychopath. In the effort to spare his life, Moody's attorneys have raised his victim's personal opposition to the death penalty in their request for clemency from Gov. Kay Ivey. 'The murder of Judge Vance was unprovoked and inexcusable. Judge Vance was, by all accounts, a devoted husband, caring father, and remarkable jurist. He was also, by all accounts, an opponent of capital punishment,' a lawyer for Moody wrote. The younger Vance said his father also upheld death sentences because he believed in following the law. 'The point to emphasize is my Dad was personally opposed to the death penalty but always made clear that his personal feelings had to give way to the law,' Vance said. ___ Associated Press writer Jay Reeves in Birmingham contributed to this report.