LAURA Castle has admitted for the first time that she shook baby Leiland-James Corkill before he died, telling a court: "I just lost my mind."

Mrs Castle said she failed to tell doctors treating the 13-month-old baby or police officers investigating his death that she had shaken him because 'I was terrified and ashamed'.

The 38-year-old defendant has admitted the unlawful killing of the baby she was due to adopt alongside husband Scott Castle, but denies murder.

But giving evidence at Preston Crown Court today, she told the jury: "I would convict me of murder based on the prosecution's evidence but I did not murder my little boy."

Through tears, she admitted she used 'a lot' of force during the incident at her home in Barrow on January 6 last year.

"I shook my beautiful boy," she said. "He was screaming. I just wanted him to stop crying."

She said as she was shaking him, she thought: "Please stop crying, I can't take it.

"I just wanted it to stop.

"He hadn't done anything to me. He was just an innocent, little boy."

Mrs Castle said Leiland-James then fell off her knee and hit his head.

Asked what her intention was when shaking him, she says: "I didn't have any intention. I just lost my mind."

The defendant admitted she had lied in her defence statement for the trial but said she was otherwise telling the truth.

Asked why she initially told a different story to doctors trying to save the child's life, she said: "I don't have an excuse, I was terrified and ashamed."  

She said she told police the truth 'but I didn't tell them everything I should have'.

"It's so hard to admit your child has died because of your actions," she said.

"He's not here because of me."

Earlier in the day she admitted regularly smacking the child, saying she herself was smacked as a child so 'I didn't really see it as an issue'. 

Leiland-James died on January 7, a day after suffering brain injuries at the home of Laura and Scott Castle in Eskdale Avenue.

Scott Castle denies causing or allowing the death of Leiland-James. The couple also deny child cruelty.

The Castles were in the process of adopting Leiland-James.

The trial continues.