The 26-year-old who German tabloids have dubbed the "Death Nurse" has admitted to killing 16 patients. Now the prosecutor's office is charging the suspect with another 13 killings. Investigators presume that six of the cases were homicide, 22 were manslaughter, and one was a case of killing on demand.

The results of autopsies have been a milestone in the investigation, according to Chief Prosecutor Herbert Pollert.

"Until about two weeks ago, the only proof we had was the suspect's confession," he said. "We found that plausible, but now we have scientific proof that the accused did indeed use the fatal medication."

The nurse began working at Sonthofen Hospital in January 2003. Investigators said the man began his series of murders one month later. He apparently stole drugs from a medicine cabinet -- tranquilizers that paralyze muscles and anesthetics that can arrest breathing. The shots he gave were deadly within five minutes. Most of the victims were older patients. Two victims were seriously ill women in their mid-40s.

The nurse said he wanted to put an end to the patients' suffering. But he also admitted that six patients were not seriously ill, such as a 73-year-old woman who had made plans with her family for the time after her release from the hospital. Thus, the prosecutor has accused the suspect of murder through devious means.

Ground-breaking

Pathologists had trouble finding traces of the medication in the victims' bodies a year and a half after their deaths. They had to be dug up from burial sites. Six of the other victims had already been cremated.

Criminal investigation chief Albert Müller said the case had broken new ground.

"We hadn't had any scientific experience with these medications before," he said. "But now we've been able to prove that the tranquilizing shots were given in very high doses right before the deaths. So we can say in these cases that suspicions have hardened."

An arraignment date has not yet been set. Police and prosecutors say a psychological report must first determine whether or not the suspect's claim that he killed out of compassion is plausible.

At the same time, Silvia Grauvogel of the German Association of Caregivers said the case raises other issues that should be addressed. The drugs the nurse is said to have used shouldn't have been accessible to him in the first place, she told DW-RADIO.

"How could a caregiver get access to such a dangerous, potent drug," Grauvogel asked. "How could it end up in that department where it's normally not used? Drugs like that are only used in intensive care units or the anesthetics department. How come no one noticed that large amounts of the drugs were disappearing?"