Mandy Burton, 22, drowned at the private care home while the assistant spent 15 minutes downstairs making the tea. As the inquest jury returned the verdict, staff at the Whitley Wood Road care home in Reading, Berkshire, walked out of the court in tears.
The inquest in Reading was told how Miss Burton was left blind, speechless and partly paralysed after her father, Kenneth, accidentally dropped her when she was just three months old.
She spent the rest of her life in care homes and moved to Whitley Wood Road in March last year, paid for by Berkshire County Council. The home is owned and run by the West Berkshire Housing Consortium.
The inquest was told by her father that she was put in the home for specialist care because she was 'a bit of a burden for my wife and myself'.
A written statement by Claire Peacock, a junior care worker at the home, was read to the jury by the coroner, Dr Joe Pim. She told how on 20 February this year Miss Burton had smiled, giggled and danced when she was told she was going to have a bath.
Miss Peacock helped her into the bath and switched on the radio. She said: 'I informed Mandy I was going to get her a cup of tea and she acknowledged what I said. I told Mandy I would be about five or 10 minutes.'
But she was sidetracked and returned 15 minutes later to find Miss Burton, who suffered from epileptic fits, submerged in the bath.
The jury heard from Michelle Riley, deputy manager at the home, that it was 'not unusual' for staff to leave residents unattended in the bath. But the manager, Jill Woods, said the first she knew about the practice was after Miss Burton's death.