Nursing manager Linda Bevan said there were "omissions in a number of areas in Paul's care".
She is now being questioned about changes since Mr Ridd's death. His special needs meant he couldn't communicate very well and nurses didn't notice how much he had deteriorated.
Nursing manager Linda Bevan says nurses should have consulted Mr Ridd's family to help recognise his signs of distress.
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The Queen has paid tribute to the spirit and dignity of the people of Aberfan, 50 years since the disaster which killed 116 children.