The former brother-in-law of murderer Jeremy Bamber is hoping that a TV dramatisation of the killings 35 years ago would help “draw a line under it”.
Colin Caffell’s ex-wife Sheila and their twin sons were shot by her brother who then staged the scene to look like a murder-suicide.
Bamber, now 58, also shot his parents June and Nevill but has always maintained his innocence.
ITV’s White House Farm dramatises the events in Tolleshunt D’Arcy, in Essex.
Bamber, who is serving a whole life term for the murders, was convicted of the killings in 1986.
Since then he has made several appeals, all of which have been rejected.
Bamber tried to convince Essex Police his sister, who suffered from mental illness, had killed her parents and six-year-old children before turning the gun on herself on the night of 6 August 1985, his trial heard.
Mr Caffell said working as a consultant on the production had dragged up emotions but he had found it cathartic and hoped the show would bring an end to the story.
“I am hoping this whole thing might draw a line under it,” he said.
“After the trial it was left to me to clear Sheila’s name and repair her reputation and the show ends with my character talking to the press saying that she wasn’t everything they had portrayed her as.”
He said he had turned down previous offers to work with people wanting to put the killings on screen but believed the writers of White House Farm were different.
“There is not the gratuitous violence you usually get in these true crime dramas, and that is my influence I think,” he said.
Mr Caffell, who is republishing his memoir of the events In Search of the Rainbow’s End, said he had never doubted his ex-wife’s innocence.
At the time she was heavily medicated and he said she “couldn’t pour baked beans on to toast from a saucepan, let alone fire a rifle”.
Bamber’s legal team requested ITV postponed the screening of the show until another stage of legal proceedings had been heard, fearing the series would “place a fictitious narrative in the public domain”.
Thousands of people have signed petitions calling for the release of documents in the case, which some believe will prove his innocence, with claims made that information was suppressed during the original trial and subsequent appeals.
Essex Police said appeals and reviews had “never found anything to suggest that Bamber was wrongly convicted of these murders 35 years ago”.
Mr Caffell said he had no doubt of Bamber’s guilt despite mistakes made at the time and put support for the killer down to his “charisma”.