A 34-year-old woman was sentenced Monday to 2 1/2 years in prison for killing her 10-year-old son by keeping him tied to a downspout on her veranda for three days, causing him to die of blood poisoning.

In an unusual move in passing sentence against Shoko Umemura, the Nagoya District Court also determined that a female acquaintance of hers who has not been indicted was an accomplice in the crime.

That woman, whose name is being withheld, denied in testimony during Umemura's trial that she was involved in the incident.