In recent times, the highest number of executions in a single day occurred on December 9, 1999.
In a rare coincidence, three US states are set to each execute a prisoner Thursday -- although each man's lawyers have appealed for a last-minute reprieve.
Facing the death penalty in Texas is Bart Whitaker, 38, who hired a gunman to kill his family. Seriously injured in the attack, his father is nonetheless one of his strongest defenders.
For years, Kent Whitaker has been moving heaven and earth to try and get mercy for his son, whom he forgave from his hospital bed.
In an exceptional turn of events, the Texas Pardons and Parole Board Tuesday recommended clemency for Bart Whitaker. The final decision lies with the southern state's Republican governor, Greg Abbott.
Meanwhile, in Alabama, Doyle Hamm is facing execution after spending three decades on death row. He was condemned to death in 1987 for the murder of a motel employee during an armed robbery.
Hamm is already dying of cranial and lymphatic cancer, and his lawyers fear execution by lethal injection would be torture, as he no longer has suitable veins.
However, after a bitter legal battle, a court finally ruled on Tuesday that Hamm's execution will go ahead, on condition that he is injected in his legs or feet -- instead of his arms or hands, as would usually be the case.
Finally, Florida is scheduled to execute Eric Branch, handed a death sentence for murdering a student in 1993.
His lawyers have launched final appeals based on the fact Branch was only 21-years-old -- and therefore, they say, cognitively comparable to a juvenile -- at the time of his conviction, nor was he sentenced to death by a unanimous jury.
Since US executions resumed in 1977, there have been 13 instances of three executions on the same day -- most recently on January 7, 2010, according to the Death Penalty Information Center.
In recent times, the highest number of executions in a single day occurred on December 9, 1999, when Oklahoma, Indiana, Texas and Virginia all executed a prisoner.
But the highest number ever was on December 6, 1862 in Minnesota, when federal authorities hanged 38 members of the Dakota people, a Native American tribe.