Daniela Poggiali, 42, was arrested after an autopsy on a 78-year-old woman who died in her care revealed dangerous levels of potassium in her system.
Since then, details of the case have been leaked slowly to the media, alongside photographs of the blond nurse smiling in holiday snaps and grinning next to apparently dead patients.
The Umberto I Hospital in Lugo in northern Italy launched an investigation after it discovered that she was on duty when 38 of 86 patients during a three month period died, while the average number of deaths when her colleagues were on duty was 10.
Potassium can stop the heart and is one of the components used in the lethal injection given to death row inmates in the United States.
Also Read
Police, who arrested her October 9, say she was the only one who could have injected the 78-year-old. But they are verifying whether others who died were killed in the same manner is difficult because the substance fades from the bloodstream after a few days.
Poggiali, who has denied murder and says she is being framed, asked colleagues to photograph her alongside patients who had just died.