The woman who abused her adopted daughter to death was sentenced to life in prison on Friday in a fatal child abuse case that shocked the country.

The Seoul Southern District Court ruled that the woman surnamed Jang, intentionally harmed her daughter, named Jung-in, dismissing her claim that the baby’s death was an accident.

The 16-month-old toddler was adopted in February and died in October last year of severe abdominal injuries and internal bleeding that were caused by “strong external force,” according to an official autopsy.

Signs of prolonged abuse, such as fractured bones and bruises in various stages of healing, were also found on her body.

“It looks like the adoptive mother stamped on the victim’s abdomen,” the court said.

“She could have predicted that impacting another blow to the victim’s already damaged abdomen could lead to her death.

“The accused started to abuse the victim habitually about a month after adopting her and caused her death with unimaginable brutality.

“As the accused ruthlessly trampled upon the victim’s dignity and honour as a human being, it is only reasonable to separate the accused from society indefinitely,” the court said.

The woman’s husband, surnamed Ahn, was sentenced to five years in prison for child abuse and aiding and abetting Jang’s violence toward their adoptive daughter.

The court reprimanded the husband for making implausible excuses that he did not know Jung-in had been physically assaulted by his wife, even though he “was in a position where he must have known” what was going on inside their home.

Ms Jang was initially indicted on charges including child abuse resulting in death.

But prosecutors later added a murder charge after reevaluating the cause of her death with forensic experts after suspicions arose that Ms Jang might have had an intention to kill the baby.

Or at least might have been aware that the girl could die from the suspected beatings and other abusive behaviours.

An investigative report aired earlier this year was a catalyst for bringing renewed attention to her case and shed a spotlight on how the police and child welfare agencies failed to prevent the tragedy despite a series of glaring warning signs.

The nation’s police chief subsequently apologised over the agency’s botched initial response and inadequate investigation.

There were three reports in the span of five months about suspected abuse toward Jung-in.

The case has unleashed nationwide grief and anger over child abuse. Hundreds of people have sent petitions to the court to demand justice for the girl.

Outside the court on Friday, protesters were calling the parents “devils” and holding signs demanding the death penalty for both of them.

“Since Jung-in died, child abuse cases have continued to happen,” said Kwon Sae-ri, who flew to Seoul from Jeju, an island off the southern coast, to participate in the protest.

“Jang should be held sternly accountable in order to prevent a similar tragedy from happening,” she said.

After the ruling was made, Lee Su-jin, who was wearing funeral clothes and holding the photo of Jung-in, cried in frustration.

“The ruling is really disappointing. If this is the punishment for abusing an innocent child to death, it will give a message to other abusers that they too could get away with killing a child.”

The head of the Korea Child Abuse Prevention Association, Kong Hye-Jung, said Friday’s ruling failed to live up to the people’s expectation to bring justice to the child.

“We will keep monitoring their second and third trials to make sure they will not have their sentences commuted,” she said.