The killer of an 81-year-old Newry pensioner has been told she must serve at least 20 years in prison before being considered for parole.Sentencing Karen Walsh, a 45-year-old pharmacist from Dublin, Mr Justice Hart said she had inflicted a brutal and sustained assault on a frail and vulnerable pensioner.Maire Rankin was found in her house in Newry on Christmas day 2008.She had been beaten with a crucifix and sexually assaulted.Mr Justice Hart said Karen Walsh\'s account of her visit to Mrs Rankin had been \'bizarre\' and one which the jury had clearly not accepted.He said Karen Walsh had offered no explanation and shown no remorse.