A convicted murderer set for execution in Texas on Tuesday has his hopes pinned on two appeals, including one challenging the state's plan to use a drug for which it will not reveal a source — as was the case with drugs used in a botched execution in Oklahoma two weeks ago. Robert James Campbell, 41, who was convicted of killing a 20-year-old Houston bank teller, would be the first U.S. inmate put to death since Clayton Lockett's vein collapsed during his lethal injection, prompting Oklahoma prison officials to halt the procedure. Lockett later died of a heart attack.