Ms McCormack and Ms Scott said every day was 'a living nightmare'
The family of a man who stabbed his mother and father to death in a "delusional attack" has criticised the hospital care he received.
Alan Scott, 36, who has paranoid schizophrenia, stabbed his mother 37 times and his father 13 times at their home in Liverpool in April last year.
His sisters have accused Mersey Care NHS Trust of not ensuring he received vital medication before their deaths.
A trust spokesman said it was offering the Scott family support.
Scott was detained indefinitely in a psychiatric hospital after admitting manslaughter on the grounds of diminished responsibility in July.
Pool of blood
His sisters, Christine Scott and Collette McCormack, said their "lives have been ruined" and every day "was a living nightmare".
Scott, who had been receiving treatment for his illness for 20 years, turned up three days late for his monthly injection of medication, his sisters said.
Alan Scott left his parents in a pool of blood in their home
He was told there was no-one available to administer it, he returned the following day - only to be told he had come too early.
Ms Scott and Ms McCormack said he then asked for a home visit, but no-one turned up until the day after he had killed their parents.
Stella Scott, 63, and her 61-year-old husband, also called Alan, were found in a pool of blood in their Allerton home.
The court was told he was so delusional at the time of the killing he falsely believed his parents were step-parents who had abused him in his childhood.
Ms McCormack said she thought the delay "directly resulted" in him killing their parents.
"Maybe if he had received his injection when he first asked for it then maybe it would never have happened and really he shouldn't have been left for so long without medication anyway," she said.
"We've lost our brother, our mum and our dad - every day is like a living nightmare."
A Mersey Care NHS Trust spokesman added: "The trust has been in close contact with the Scott family and has provided information about the trust's own investigation and offered them support."