The seven-week-old baby suffered a heart attack. His brain was damaged and he had died within two days of admission to Grantham District Hospital.
Physiotherapists who had cleared his breathing told the court that they were 'stunned' and 'devastated' by Liam's death.
The nurse in charge of his ward had thought Liam well enough for her to begin a meal break just a few minutes before his heart stopped. One of Liam's doctors said his illness had not been life threatening and he showed no symptoms of a bad heart.
On the third day of the trial jurors were told how Ms Allitt, 24, had special responsibility for Liam. The prosecution claims she 'did something to him'. She denies murdering Liam and pleads not guilty to three other charges of murdering young patients and 11 charges of attempted murder.
Chris Taylor, Liam's father, said Ms Allitt had met him and his wife when they brought their son to ward four, the children's unit at the Lincolnshire hospital. Liam was 'poorly', but nothing was so drastically wrong with his bronchial condition that prevented the Taylors returning home for about 90 minutes.
When they came back to the ward, Ms Allitt told them Liam had been 'violently sick across the room'. His vomit had been 'yellow like the curtains', Mr Taylor said, and Ms Allitt had told him Liam would have died if at home because of the breathing difficulties he had suffered. She had needed to change her overalls because they were soaked in vomit.
But Margaret Geeson, senior staff nurse on the ward, said Ms Allitt had not told her of Liam's vomiting or respiratory troubles. 'If I had been told, I'm sure I would have remembered. It was something I would have acted on,' Mrs Geeson told the jury.
The Taylors had returned to find Liam 'lifeless, just laying there', and were at his bedside throughout the night of 21 February 1991. The following morning he had improved and opened his eyes. 'He reached for a teddy bear,' Mr Taylor, said. Liam seemed '100 per cent better'.
The court heard that Ms Allitt came on duty that night. Mr Taylor felt confident enough to go to bed after midnight in a parents' room on the ward. By five o'clock, he had been woken with the news of Liam's heart attack.
Dr Harshad Tailor had admitted Liam with a 'moderate infection of the respiratory system'. He was 'much worse' when Dr Tailor saw him later but, by 9pm on 21 February, was 'much better'.
Jenny Starling, one of the physiotherapists clearing Liam's chest with suction catheters (tubes), made a routine visit to him at 9.30pm on 22 February, less than seven hours before his heart attack. She cleared his lungs, and Liam seemed improved, the court was told. But within hours, she was summoned urgently. She found Ms Allitt alone with Liam. He had deteriorated - 'a very, very poorly baby', Mrs Starling said. 'I was very surprised.'
She began again to remove mucous and left Liam 'very much better' at 3am. Mrs Starling said Ms Allitt had not been using suction catheters on Liam, but other witnesses said she had asked for colleagues to fetch extra supplies of catheters.
Liam deteriorated around 4am on 23 February. Charge nurse David Wiles said he had been asked by Ms Allitt for more catheters. He had left Liam's room to order some when, he told the court, Ms Allitt said: 'Mr Wiles quick, he's gone all white and blotchy.'
A specialist team arrived quickly, but Liam's heart had begun to give out, the court heard.
The trial continues today.