A 26-year-old German nurse was charged with murder over the deaths of 29 of elderly patients at a Bavarian hospital.
The nurse, whose name was not released, was charged with 16 counts of murder, 12 of manslaughter and one count of mercy killing, prosecutors in the town of Kempten said.
He could be sentenced to life imprisonment if convicted.
The deaths at a hospital in nearby Sonthofen took place between March 2003 and July 2004. Prosecutors say 17 female and 12 male patients aged between 40 and 94 died.
Most of the patients were older than 75 years, but they also included two gravely ill women aged 40 and 47, police have said.
At the time of his arrest in July 2004, the man admitted to some of the killings, saying he was trying to spare the patients senseless suffering, prosecutors said.
But autopsies of the bodies showed that not all were seriously ill, and he was charged with murder in the cases where it is believed he "arrogantly" made a decision over life and death, prosecutors said.
The nurse was also charged with two cases of causing serious bodily harm, including allegedly injecting a 22-year-old soldier with an unknown substance after she was hospitalized following an accident.
The nurse was also charged with five counts of theft for allegedly taking a computer, fax and other items from hospitals in Ludwigsburg, Kempten and Sonthofen.
According to police, the man used a mixture of the sedative midazolam, the anesthetic etomidate and the muscle relaxant lysthenon to kill the patients.
Police tracked down the nurse as they investigated reports that the drugs were missing and compared the times when patients died to the hours he worked. Investigators found unsealed vials of the medicines at his apartment.
Authorities are also investigating the person responsible for the medications at the Sonthofen hospital to determine whether they were properly supervised, the AP reports.