He acknowledged that in several cases he had been overwhelmed by caring for the people involved

Investigating magistrate

The nurse, who has been dubbed the "Angel of Death", said he acted out of sympathy for the patients' suffering.

Twelve of the killings are reported to have taken place in a home for the elderly in the central district of Obwalden.

Suspicious deaths

The nurse, who is from Lucerne district, was arrested in June after deaths in a nursing home aroused the suspicions of the authorities.

The man drugged his victims with painkillers, or suffocated them with a plastic bag or a pillow, according to a statement issued by the investigating magistrate and local police.

The Netherlands legalised euthanasia earlier this year

"As far as his motive goes, he is sticking to his previous comments that he acted out of sympathy, compassion, empathy and salvation of the people involved," said the magistrate, Orvo Nieminen.

"On the other hand, he also acknowledged that in several cases he had been overwhelmed by caring for the people involved. He added that in some cases he felt relieved, somehow liberated, after the person had died."

Mental health tests

The man is to undergo psychiatric tests before the investigation continues.

Police say all of the killings took place between September 1995 and June this year and were carried out in retirement homes in the Lucerne, Obwalden and Schwyz districts.

Euthanasia is tolerated in a number of Swiss cantons, provided strict rules are followed.

According to national law, active euthanasia is illegal but is not regarded as a crime if a doctor administers lethal drugs to a person close to a painful death for his own use.