Japan's top court on Friday acquitted a former Vietnamese trainee of abandoning her stillborn twins, overturning lower court rulings that sentenced her to a suspended prison term.

In the first finalized ruling concerning the abandonment of a stillborn child, four judges on the Supreme Court's Second Petty Bench unanimously ruled that the acts committed by Le Thi Thuy Linh, 24, did not amount to the crime of corpse abandonment.

Following the birth of her stillborn twin boys in November 2020, Linh placed their bodies in a cardboard box and left them on a shelf in her room for around 33 hours, along with a letter of apology.

Le Thi Thuy Linh's supporters celebrate as a lawyer holds up a banner reading "not guilty" in front of the Supreme Court after its ruling on March 24, 2023, in Tokyo. (Kyodo)

The court ruled that such actions are "not considered incompatible with customary burial practices," and thus did not constitute corpse abandonment.

Linh said at an online press conference following the ruling, "I am happy from the bottom of my heart. I hope Japan will change into a society that understands the concerns of pregnant trainees and women so they can give birth with ease."

The government-sponsored technical internship, introduced in 1993 under the premise that it helps to transfer skills to developing countries, has faced criticism over reports that foreign trainees who got pregnant while in Japan were deported.

The top court's decision is likely to impact ongoing discussions on revising the system, which has also been criticized as being used as a cover for companies to import cheap labor.

Linh gave birth to stillborn twin boys at her home in Kumamoto Prefecture, southwestern Japan, where she had been working as a trainee on a mandarin farm. The stillbirth was only discovered when she was taken to a hospital the next day.

During the trial, Linh said that she planned to hold a funeral for them but had not known what to do given the severity of the situation. She also said she had not revealed to anyone that she was pregnant for fear of being deported.

Her defense argued that she had only "temporarily laid them to rest" and that Linh's actions "were the best she could do for a woman who had given birth alone in a foreign country."

Prosecutors stressed that Linh believed at the time she would be forced to leave Japan if she was discovered to be pregnant or to have given birth, arguing that the act of concealing the bodies in two layers of boxes was "far from mourning."

In earlier rulings, both the Kumamoto District Court and the Fukuoka High Court found her guilty, with the latter sentencing her to three months in prison, suspended for two years, in 2022.