Francisco Beltran, for the defence, told the jury his client was in "total disagreement" with the charge of murder against him.
"He has committed no crime, and it goes without saying that he has not committed the crime of murder," Mr Beltran said.
He asked the jury of nine to see his client as a "sick man" who had been living in the street without a diagnosis or treatment for his acute schizophrenia. Answering questions in Bulgarian with the help of an interpreter, Deyanov told the court he is haunted by voices which tell him how to act.
He claimed they were telling him he was "an angel of Jesus Christ who is going to create a new Jerusalem".
"They direct how I act, sometimes they say kill, fight, hit, pray," he said.
More top news
The man was left with a permanent brain injury after he was given double the intended dose of radiotherapy as a teenager over 20 years ago.
Turning colder again over the next few days.
Serial paedophile Barry Bennell was branded "the devil incarnate" by a judge who sentenced him to 31 years for abusing 12 young footballers.