The scheduled July 14 execution of a man convicted in the slaying of a medical student robbed of $40 has been postponed indefinitely.

A Texas prison system spokesman said Wednesday that a state district judge in Houston has withdrawn the execution order for Perry Eugene Williams pending test results for the drugs to be used in his execution. The Texas Attorney General's Office had agreed in a lawsuit filed on Williams' behalf to have the drugs tested before his execution.

Williams is set to die for the 2000 slaying of Baylor College of Medicine student Matthew Carter.

Texas Department of Criminal Justice spokesman Jason Clark says the delay doesn't affect the state's next scheduled lethal injection, the Aug. 10 execution of Ramiro Gonzales for the 2001 slaying of an 18-year-old woman in Medina County.