Devastated mum screams “scum” as her husband admits killing their baby.

A Perth father has pleaded guilty to manslaughter over the death of his seven-month-old girl, Lily.

Paul James Cosgrove, 24, was charged after his seven-month-old daughter was found unconscious at their house in September last year. He was initially charged with causing grievous bodily harm, which was later upgraded to manslaughter.

In court yesterday, in front of his estranged wife and family, he finally pleaded guilty.

Lily Cosgrove. Via Facebook.

Cosgrove had previously claimed that Lily received her fatal injuries by falling off her change table.

He phoned his wife, Emma who had left for work early that morning to tell her that Lily was not well after the fall. Ms Cosgrove rushed back to their Ellenbrook home and when she found Lily, their only child, unconscious she dialed triple-0.

Lily was rushed to hospital but to her mother’s despair she died two days later

The seven-month-old had swelling on her brain from an injury believed to have been inflicted by her father hours earlier.

Emma Cosgrove said that she was devastated. Via Facebook.

"No one could save her," Ms Cosgrove told reporters at the time.

"She had brain damage.

"I'm in shock really. I still can't believe my baby girl's not here... that this morning I didn't see her face looking at me with a smile first thing in the morning.

"She was just too perfect and too happy and too good [for this world]."

In court yesterday  Paul Cosgrove entered a guilty plea. Via Facebook.

Major Crime Squad detectives were called to investigate Lily's injuries and after an investigation charged Mr Cosgrove with grievous bodily harm.

In court yesterday, nearly year after Lily died Paul Cosgrove entered a guilty plea.

The ABC reports that as he admitted the charge Emma Cosgrove’s family wept and one woman yelled "you low life piece of shit.”

Emma Cosgrove, wearing a T-shirt with a picture of Lily on it and the words “I love you mummy” screamed at the man she once loved calling him “scum”.

In tears all she could say was “my baby, my baby” repeatedly as she left the courtroom where her husband made his chilling admission.

Lily died in hospital. Via Facebook.

Emma Cosgrove told The West Australian that she misses Lily “painfully.”

"Lily is and always will be my best friend,” she said.

“I still ask everyone to pray she’s happy and safe and we will be reunited again when it’s my turn."

Emma Cosgrove called her husband "scum" as he admitted killing their daughter. Via Facebook.

Last month in a heartbreaking tribute on Facebook she wrote:

"10 months and 1 week ago today I held my daughter and watched her slip away into heaven because there was nothing I could have done to protect her. I even wanted her if she was a blind vegetable and I had to change her nappy for the rest of her life."

"The utter guilt and despair I feel every day is torture and hell from the moment I wake up in the middle of the night till I try for hours to get to sleep at bedtime when I tell her how much her mummy loves and misses her so much and I cant wait to be with her again."

She continued: "There's not a day goes by I don't cry or that I'm not so angry with myself. I miss my best friend so much it feels like I'll vomit and now I sit around like a useless twat with no daughter or husband to look after, no house I can say I built, no dream Maldives holiday pics to look back on that we saved for.”

Cosgrove will be sentenced in the Supreme Court on December 6. Via Facebook.

Yesterday Emma Cosgrove told reporters that she would “never forgive herself” for going to work and leaving Lily alone with her father.

“Whatever sentence (Cosgrove) gets, my baby will never wake up,” she said outside court.

Cosgrove will be sentenced in the Supreme Court on December 6.