• Sean Sadler was in a relationship with the toddler's guardian when he killed her
  • The baby girl had a tough start to life as she was born to a heroin addict mother
  • Murderer Sadler will be sentenced Friday

A male babysitter who battered and shook a 21-month-old baby girl, leaving her with brain injury and broken ribs, has been found guilty of murder.

Sean Sadler, who was in a relationship with the baby's special guardian at the time of the crime three years ago, denied murdering her but was convicted by a U.K. court Wednesday, said a report by ITV.

Sadler called the emergency services on Nov. 19, 2017, claiming baby Lilly had fallen asleep and wouldn't wake up. She was rushed to the Birmingham Children's Hospital, where she was put on life support. She died three days later.

Prosecutors reportedly told the jury at Birmingham Crown Court that Lilly had been "forcibly shaken" and possibly thrown against a surface like a settee's armrest. During the trial, experts testified that Lilly had suffered a total of 40 injuries, including 20 to her head and neck. She also had severe injuries on her body and limbs.

"When her hair was shaved, several bruises were found on the top of her scalp and further grip marks on both of her thigh. Medical investigations revealed extensive bleeding into the back of her eyes," Prosecutor Jonas Hankin was quoted as saying to the court.

The court also heard from the West Midlands Police, who said the postmortem examination found three broken vertebrae in her spine and bleeding in her lungs from an injury caused at least three weeks before the death.

Many of the wounds were consistent with the child being slapped and or gripped with excessive force, the police further said.

After Sadler began a relationship with Lilly's guardian, the court heard that he became a regular visitor and sometimes would stay overnight. She trusted Lilly with him and soon started leaving the child in his care.

However, the guardian became concerned after bruises started appearing on Lilly's body. She took the child to a hospital, but no concerns were raised about abusive handling.

She then approached Lilly's nursery and asked them to monitor her, but nothing out of place was noticed there too, the court heard.

Born on Feb. 21, 2016, Lilly had an especially tough start to life as a heroin addict birthed her. She was put into her grandmother's care before the special guardian took over.

The nursery staff described Lilly as a child with no serious health problems and as a "happy and bubbly child who always had a grin and was always on the go."

Sadler is due to be sentenced Friday.

Child Abuse
Representational image Reuters