Ms Costello faces up to 10 years in prison for conspiracy to defraud the government and up to five years for social security fraud.

'Working all angles'

Prosecutor Norman Barbosa described how she took her children to medical and social security appointments, persuading them to pretend that they could not talk, read or dress themselves.

Her son Peter was coached from age eight, her daughter Marie from age four.

She never had a job and moved regularly from flat to flat, the prosecutor said.

She then claimed benefits as a carer for five years when they had reached adulthood, despite the fact that both had left home.

"She was working all angles," Mr Barbosa said, quoted by The Columbian newspaper.

The family was found out only after Peter Costello was caught on video defending a traffic ticket in a local court.

He was found to have driving licences under fake names in three states.