GRAPHIC WARNING: A Sydney woman who chopped her mum's head off with kitchen knives has been sentenced to 21 years jail over the gruesome killing. She had pleaded not guilty to the 57-year-old's murder due to mental impairment. The trial was told the pair were arguing when Camilleri - who had a history of refusing to take her psychiatric medication - set upon her mother with kitchen knives, only stopping the attack when her head fell off and her eyeballs popped out of their sockets. Rita Camilleri. Jessica Camilleri will spend at least 16 years and two months behind bars. Justice Helen Wilson, SC, said the decapitation must be regarded as one of the most serious instances of manslaughter as she detailed Mrs Camilleri's terrifying final moments.