Los Angeles A former Los Angeles area hospital worker who told police nearly three years ago that he was an "Angel of Death" who secretly killed patients with lethal injections, pleaded innocent in a state court on Friday to six murders. Efren Saldivar, 31, entered his plea before Los Angeles superior court Judge Michael Kellogg through his public defender. He is due back in court on March 30.

Prosecutors said Saldivar, a former respiratory therapist who in February of 1998 offered a detailed confession to more than 40 murders at Glendale Adventist Medical Center over a five-year period during the 1990s -- then recanted it -- may face the death penalty if convicted.

Saldivar told police during his initial confession that he killed terminally ill people by injecting them with pavulon, a drug that stops patients from breathing. He was arrested last month after authorities found pavulon in the exhumed bodies of six elderly patients who died on his watch in 1996 and 1997.

The criminal complaint against Saldivar, who is being held without bail, charges him with killing the six people by administering pavulon to them.

The drug is normally given to patients who are going to be placed on a respirator. Five of the six patients he is accused of killing were not given the drug as part of their regular treatment.

Saldivar, who worked at the hospital on and off for eight years, initially told police that he killed only those patients who were unconscious, had a "do not resuscitate" order on their charts and appeared close to death.

But he recanted shortly afterward, telling a national TV audience that he confessed to crimes he did not commit because he was severely depressed and wanted to be put to death.