A MUM “romped” with her baby’s killer in hospital as doctors prepared to switch off the dying tot’s life support.

Catherine Davidson had “intimate relations” with ex-soldier Gordon McKay, 38, as her five-month-old daughter Hayley lay dying in hospital.

Davidson has admitted responsibility for the tot’s death after shaking her vigorously at his home in Buckhaven, Fife on Valentine’s Day in 2016.

He pleaded guilty to a reduced charge of culpable homicide at the High Court in Livingston and now faces an “inevitable” prison sentence.

Little Hayley suffered a severe brain bleed when McKay shook her — and later died in hospital.

A family liaison officer walked in on Catherine “romping” with McKay in a family room at the hospital when she went through to advise her that Hayley’s life support machine was about to be switched off.

Prosecutor Jane Farquharson told the court: “At the time of Hayley’s death, Mrs Davidson held her daughter in her arms - after a few minutes she indicated she needed to be with Mr McKay.”

She added the mum “seemed more concerned for the welfare of, and attentive to, Mr McKay” than tending to the needs of her critically injured daughter.

The court heard how Catherine had developed an “obsessive” relationship with McKay around the time of her daughter’s death.

The pair had denied they were seeing each other but forensic tests showed they had smoked cannabis together with Hayley in the room the night before the youngster was fatally injured.

On the morning of her death, Catherine left the tot alone with him for an hour while getting her two older daughters ready for a family day out.

After an hour, she received a text from McKay saying: “Come quick”.

Ms Farquharson said: “Mrs Davidson walked into the living room where she found the accused leaning over her daughter Hayley, administering CPR.”She describes screaming at her partner: ‘What happened?’ He replied: ‘Phone an ambulance, she’s not breathing’.”

Paramedics, who arrived within seven minutes, found Catherine in a distressed state and McKay giving CPR to Hayley, who was “pale, floppy and unresponsive”.

Before the ambulance had arrived, McKay told his partner he had left Hayley alone to run a bath.

Ms Farquharson added: “When he returned to check on Hayley she had wriggled down the beanbag. He stroked her face and found her unresponsive.

“Mr McKay then described picking Hayley up and giving her a shake.”

In response to police questioning at hospital, Ms Farquharson said he described shaking the baby three or four times by holding her shoulders.

She explained: “He described her head as whipping backwards and forwards.

“The bleed to her brain was not a slow one and Hayley’s symptoms would have been obvious following injury.

Medical experts diagnosed a “non-survivable head injury” and, on February 17 after brain stem tests confirmed no activity, care was withdrawn and Hayley died.