Photo/IllutrationHiroyuki Kawakami, left, and Masashi Akita, the lawyers for Yasuko Yamauchi, speak with reporters on Oct. 25 after the Osaka High Court found their client was not guilty. (Yuto Yoneda)

OSAKA--A high court here on Oct. 25 overturned the conviction of a 69-year-old woman in the death of her 5-month-old grandchild and raised doubts about traditional methods used to determine shaken baby syndrome.

Yasuko Yamauchi had been given a five-year, six-month sentence after being found guilty by the Osaka District Court of inflicting bodily injuries resulting in death.

But the Osaka High Court overturned that ruling after questioning whether a simple application of the three main symptoms of shaken baby syndrome should be used to recognize that physical abuse was involved in the death of a child.

Yamauchi was initially accused of causing a strong impact to the back of the head of her 2-month-old granddaughter in April 2016. At the time, she was at her daughter’s home in Higashi-Yodogawa Ward in Osaka city, taking care of the infant.

Yamauchi was arrested and indicted after the granddaughter died three months later.

The grandmother has always maintained her innocence, but the Osaka District Court found her guilty on grounds the baby showed all three major symptoms of shaken baby syndrome: subdural hematoma, retinal bleeding and swelling in the brain.

The district court also said Yamauchi was the only person at the scene capable of inflicting the injury.

However, the Osaka High Court used evidence provided by two neurosurgeons to rule that the baby might have developed cerebral venous sinus thrombosis, a condition in which a blood clot occurs in the brain and eventually leads to a stroke.

The high court said the three shaken baby syndrome symptoms may have led doctors to fail to diagnosis the condition, which could have caused the baby’s death.

The high court also said Yamauchi showed no signs of undue stress from taking care of the child and ruled it was “highly unlikely” that, given her small frame, she could have inflicted the violent shaking of the baby.

Therefore, reasonable doubt remained on whether Yamauchi committed an act that led to injury, the ruling said.

Lawyers for Yamauchi and other legal experts said the ruling could lead to a review of how shaken baby syndrome cases are dealt with.

The lawyers, including Masashi Akita, belong to a project group that has been looking more closely at shaken baby syndrome cases.

Group members said that at least three not guilty verdicts have been handed down in such cases since autumn 2017.

“This ruling also covered the manner of deciding cases that concludes abuse was involved based solely on medical observations,” Akita said. “There will be a need for a fundamental review of how investigative organs and child consultation centers deal with such cases.”

Hirotaro Iwase, a professor of medical jurisprudence at Chiba University, said the ruling highlighted the danger of recognizing shaken baby syndrome based only on the three main symptoms.

“It has not been proven scientifically that violent shaking alone causes shaken baby syndrome, and the views among experts are divided,” Iwase said. “I feel the ruling is an appropriate one.”

(This article was written by Takashi Endo and Yuto Yoneda.)