Saenz was born in 1974 and worked at the DaVita dialysis centre in Lufkin, in east Texas, having previously been dismissed from other nursing posts. Dialysis patients are connected to a machine by lines through which their blood circulates, and the machines and lines are cleaned with diluted bleach.
Between January and April 2008 the clinic had an extraordinary number of patients collapse during treatment. Far more emergencies in four months than in the previous several years combined. Five died: Clara Strange, Thelma Metcalf, Garlin Kelley, Cora Bryant and Opal Few. Ten more were injured.
On April 28, 2008 two patients undergoing dialysis saw her draw bleach into a syringe from a cleaning container and inject it into the lines of two other patients. They reported it that day, and the clinic was closed and the state notified. Syringes recovered from the clinic's waste tested positive for bleach and for the patients' blood.
She was convicted on March 30, 2012 of capital murder in the five deaths and of aggravated assault on the survivors, and sentenced to life without parole on April 2, 2012. The prosecution did not seek death.
She has maintained her innocence, and the appeals have focused on the scientific evidence for detecting bleach in blood, which was novel and was contested at trial by both sides' experts. That dispute is genuine and unresolved in the literature, and it sits alongside the direct eyewitness evidence of two patients who saw her do it.