“I have nothing to hide,” John Doyle, 49, told the High Court in Edinburgh.
He described his teenage sister as “annoying but in a cute way”, but admitted that in the weeks leading up to her death - more than 27 years ago - they had been growing apart.
The trial has heard that Elaine was found naked and strangled just yards from her Greenock home early on June 2 1986.
Mr Doyle, just short of his 22nd birthday at the time, said he was wakened by the sound of police walkie-talkies in the Ardgowan Street house.
“There were two police officers in the house. My mum was running about greeting. My dad was in a state and the police were describing the circumstances of what had been going on next to the house.
“That a body had been found.”
Mr Doyle also said he was “feeling rough” that morning. He had a hangover after drinking the night before.
The court heard of how he went with his father, postman Jack Doyle - who has since died - to identify Elaine’s body.
John Doyle had to be helped down steps because he was walking with the aid of crutches and his ankle was in plaster after being crushed in a hit-and-run accident.
The accused, John Docherty, 49, denies murder - and has given the court a list of 41 possible suspects which, he claims, might include the real culprit.
John Doyle’s name is one of those of those on the list.
Advocate depute John Scullion, prosecuting, asked Mr Doyle: “In the early hours of 2 June 1986 did you leave the family home?” Mr Doyle replied: “I did not.”
“Did you kill your sister?” the prosecutor continued. “I did not,” repeated Mr Doyle.
The suggestion was “ridiculous,” he added.
Questioned by defence QC Donald Findlay, Mr Doyle said: “We were just normal brother and sister.”
But he said: “She was going her way and I was going mine.”
The trial heard that in a later statement to police, John Doyle said: “When Elaine died we weren’t really talking to each other.”
The statement continued: “To be frank we would disrespect each other.
“We would get on each others’ nerves and I would see her as my annoying little sister.”
Mr Doyle protested that that should not be taken literally.
“She was annoying in a cute way,” he told the trial.
Docherty, now of Hunters’ Quay, Holiday Village, Dunoon, denies murder and claims that at the time he is alleged to have stripped and strangled 16-year-old jeweller’s assistant Elaine he was with his parents - who are no longer alive - at their home in Anne Street, Greenock.
The charge alleges that on June 2 1986 in a lane near Elaine Doyle’s home in Ardgowan Street, Greenock, he seized her by the hair, struck her on the head and either removed or compelled her to remove her clothing.
The charge goes on to allege that Docherty forced Elaine to the ground, pushed her face into the ground, sat or knelt on the teenager then placed a ligature round her neck and strangled her.
Docherty also denies stealing a handbag from Ardgowan Street on the same date.
He further denies a charge of attacking another woman, Linda Hargie, on various occasions between 1990 and 1995 at an address in Anne Street, Greenock by seizing her and pushing her and punching her on the head.
The trial continues.