Dr Ann Biezanek, 65, said her daughter Lucy had had an intractable illness for 13 years. No medicine worked, but cannabis made Lucy feel life was bearable and 'eased her pain'.
Dr Biezanek told Liverpool Crown Court she took responsibility for getting the drug because Lucy needed it, but could not risk buying it herself because she was on bail.
'I became a criminal because my conscience said that it would be wrong of me to continue to obstruct her. I was following a higher moral law,' Dr Biezanek said.
Lucy,33, was arrested while living in Scotland and a bail condition was to be of good behaviour and return to her mother's Wirral home, Dr Biezanek, a locum general practioner and homeopath, said.
Asked whether she had bought the cannabis from dealers in pubs, houses or on street corners, Dr Biezanek replied: 'Wherever I could find them.'
The court heard that police officers raided her home in February this year and found almost two grams of the drug in Dr Biezanek's handbag. Dr Biezanek, of Wallasey, Wirral, denies five charges involving supplying, attempting to supply and possessing cannabis.
The case continues on Monday.