Barnes was found hanging in his cell at HMP Hewell on January 25, 2015.
At the time of his suicide in the Redditch prison Barnes was still on trial at Wolverhampton Crown Court, accused of battering 80-year-old grandmother Cynthia Beamond to death with a saucepan at her Halesowen home, and then killing 67-year-old Philip Silverstone with a car jack at his flat in Belsize Park, London.
Following the five-day inquest at Worcestershire Coroner's Court in Stourport, the jury returned a conclusion that his death was suicide.
Barnes, aged 33 and from Birmingham, was found hanging in his cell at about 6.05am on Sunday, January 25.
He had been due to be cross-examined by prosecutors on the Friday before, but didn't appear in court after complaining of feeling ill.
During the inquest before Coroner Geraint Williams this week, a member of Barnes' defence counsel, Joseph Kotrie-Monson, said Barnes had told him he wanted to take his own life.
However evidence was also heard from the senior custody officer at the crown court, Marie Dance of prison transportation and custody company GeoAmey, who came into contact with Barnes over six days while he was on trial.
She said Barnes was asked 'on every day' about his mental state, and told the inquest: "I spoke to Mr Barnes and he stated to myself that he had no thoughts or issues at present."
Forensic psychatrist Dr Dinesh Maganty, who saw Barnes in the weeks leading up to his suicide, also gave evidence during the inquest and stated:
"With others who are depressed it is much more straight forward. We can see there is certain behaviour, they can't hide the symptoms, they can't hide the difficulties. That would not be the case with Mr Barnes. He could hide his symptoms."
He added: "Mr Barnes was by any stretch of the imagination not what you could describe as normal."
Barnes was on trial for the murder of Mrs Beamond, who was bludgeoned to death in her home with a saucepan and her body hidden in her home.
His other alleged victim, Mr Silverstone, was found dead and covered in blood by a carer at his Belsize Park flat.
His elderly wife, who suffered from dementia, had been left alone with his lifeless body for more than 30 hours by the time he was discovered.
Barnes knew both victims - he had met Mrs Beamond growing up as his grandparents lived on her street in Juliet Road, Halesowen.
Mr Silverstone was a former neighbour. Barnes denied both killings.