A father has admitted to being responsible for the eventual death of his daughter, 18 years after he was jailed for severely bashing her as a child and leaving her permanently disabled.

WARNING: Some readers may find details in this story distressing.

In 2005, Terrence Bice was sentenced to five years in jail after he pleaded guilty to causing grievous bodily harm to the then two-year-old, Teagan Ferguson, who he threw across the floor because she would not stop crying.

Teagan was left with permanent brain damage and in need of constant care.

Bice was charged with her murder in 2021 after she died in 2020, aged 18, after spending five years in palliative care.

Injuries led to death: police

In a statement, police alleged the injuries she suffered in 2005 led to her "developing numerous chronic health conditions, which directly impacted on her quality of life ... (and) eventually led to her death."

The 41-year-old had pleaded not guilty to the murder charge and had been due to stand trial in the Supreme Court in July.

However, today when Bice appeared in court via video link from prison, state prosecutor David Davidson revealed the murder charge was going to be discontinued and replaced by the lesser offence of manslaughter.

Once that happened, Bice then pleaded guilty to unlawfully killing Teagan in June 2020, when she died.

It is believed to be among the first cases of this kind under WA laws in Western Australia following changes to the sentencing laws, which allow people who have already been sentenced for a related offence to be also convicted of causing the death of a person.

Teagan's mother Kirsty, who was her primary carer, was in court for the hearing accompanied by a group of supporters.

Bice was again remanded in custody, until he faces a sentencing hearing in August.