Bernard Bradley, 51, was answering questions about a night at a disco in Greenock more than 27 years ago.
The following morning Elaine's naked body was found just yards from her home in the town's Ardgowan Street.
On trial at the High Court in Edinburgh is John Docherty, 49, who denies stripping and strangling Elaine, 16, on June 2, 1986.
As part of his defence, Docherty has produced a list of 41 possible suspects which, his defence team suggest, might include the real killer.
On the list is Mr Bradley, who in 1986 lived in Larkfield.
Yesterday Mr Bradley described his night at a disco in the Celtic Club in Greenock's Laird Street.
He danced with all of the girls at a table where Elaine was sitting with her pals.
The trial has heard he was the only man seen dancing with Elaine, who spent much of the night on the dance floor with three girlfriends.
Afterwards one of Mr Bradley's friends drove him home, stopping on the way at a Chinese takeaway.
He thought he arrived home about 11.30pm. Mr Bradley said: "I just went to bed."
Advocate depute John Scullion, prosecuting, asked him: "Did you go back out? Did you go to Ardgowan Street?"
Mr Bradley told him no.
Asked what he thought about his name being on the list of "incriminees", Mr Bradley replied: "It is ridiculous."
He added: "I know who I was with, where I went, who I went with."
Defence QC Donald Findlay suggested that, if he had wished, Mr Bradley had plenty of time to leave his home in Devon Road and return to Green-ock town centre where Elaine was with her friends near a hamburger stall until around midnight.
"I know where I was and what I did," said Mr Bradley. "I know I was at home."
He told the lawyer: "It could not have happened. I was at home. I went home with a friend."
Mr Bradley said he did not know Elaine and only became aware of her death when police visited him on the day her body was found.
The trial also heard that in 2008 when police re-opened the murder investigation they visited Mr Bradley again and he gave them a sample of his DNA.
The trial continues.