A former nurse who murdered three patients by contaminating their intravenous drips with disinfectant was sentenced to life in prison on Tuesday by a Japanese court, according to local media.

During her trial, 34-year-old Ayumi Kuboki admitted to killing the patients in their 70s and 80s five years ago in a case that shocked Japan.

She had previously told police she may have killed 20 people over just two months, but later told prosecutors she could not comment on that during the trial.

The presiding judge at the Yokohama district court said he had considered handing Kuboki the death sentence, public broadcaster NHK reported.

"She said she regrets (her actions) and wants to pay for her crime. There's a chance she will be reformed, and I couldn't help but to hesitate over choosing a death sentence," the judge said.

Court officials were unavailable for comment on Tuesday afternoon.

Japan, where more than 100 inmates await execution, is one of the few developed nations that still have the death penalty.

Prosecutors had demanded a death sentence for Kuboki but the nurse's lawyers reportedly argued that she suffered depression due to stress over the deaths of her patients, and had diminished capacity.

Kuboki had told the court she did not want to be blamed by family members when something wrong happened to her patients when she was on her shift, and felt "relieved" when one of the victims died, NHK said.

The son of one of the victims said he was not happy with the ruling, according to the broadcaster.

"She killed innocent people with selfish motives and she's not sentenced to death. It's wrong," he said.

Public support for capital punishment in Japan remains high despite international criticism, including from rights groups.

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