Frances Newton, 39, was to have been killed by lethal injection last night for the murder of her husband and two children in 1987. But Texas governor Rick Perry agreed a four-month stay after the Texas board of pardons and paroles recommended a delay so that the defence could make its case that Ms Newton was wrongly convicted.
Mr Perry said the delay should not be taken as an indication of innocence, but would be used to retest gunpowder residue on the skirt the defendant wore at the time of the murders.
In May, Mr Perry rejected the board's suggestion to commute to life in jail the death sentence of a mentally ill killer, who was then executed. But in March he followed the recommendation to commute another sentence to life.