Pike, 50, survived two injections of the normally lethal substance pentobarbital. Tennessee prison chief quits after failed execution of Christa Pike Key points and original sources are listed below.

• Pike, 50, survived two injections of the normally lethal substance pentobarbital.S1

• Tennessee prison chief quits after failed execution of Christa PikeS2

• Frank Strada, who oversaw the process that left Christa Pike unconscious and hospitalized, quit as an independent review begins.S3S6

• Pike was placed on a ventilator and remained unconscious in a hospital, her attorneys said FridayS4

• The Tennessee prison chief who oversaw the botched execution of murderer Christa Pike has stepped down from the position.S5