Brian Geddes shed a tear of joy and relief when the Renee MacRae murder trial ended with the jailing of her callous killer William MacDowell.
But almost a year on from that poignant moment, he knows there is still “unfinished business” and he has yet to complete the second part of the two-pronged investigation.
The bodies of Renee and her three-year-old son Andrew have never been recovered.
MacDowell died five months after being convicted without revealing where they were hidden.
The search will continue, but Detective Chief Inspector Geddes fears that hopes of ever finding Renee and Andrew may have died with the killer.
BBC Murder Trial: Behind the scenes
The case gripped Scotland over the 46 years since the pair disappeared on November 12 1976.
Renee’s burned-out BMW was later discovered in a lay-by on the roadside of the A9.
A series of police investigations had failed to bring the killer to justice.
That was until last September when MacDowell was found guilty at the High Court in Inverness.
The climax of what was one of the biggest unsolved murder cases in Scottish legal history is told in a new two-part documentary series to be aired next week.
Murder Trial: The Disappearance of Renne and Andrew MacRae will be screened on BBC Scotland on August 22 and 28.
The programme was given behind-the-scenes and in-court access to the case and its dramatic conclusion for police and Renee’s family.
MacDowell was always in the frame for the murders of his secret lover and their son, but proving his guilt was difficult.
As prosecution KC Alex Prentice said in the lead-up to the trial: “This case is fairly unique. There is no direct evidence of the killing or even of the removal of the bodies from the lay-by.
“But there is a vast array of segments of evidence which, I suggest, when combined together, would form a coherent and convincing case against the accused.”
Growing up with the infamous murder case
When the majority verdicts are announced, DCI Geddes is seen wiping away a tear.
He was two years old when Renee and her son disappeared and grew up knowing about the case he was later to lead when it was re-investigated.
He broke a habit of not attending the conclusion of cases to join Renee’s family and friends for the verdict.
The conviction, he felt, was a moving experience for them, as well as the officers who worked for five years on the re-investigation and those who previously worked the case.
“It was special, but it was emotional. We’re seen as these gruff detectives who don’t show emotion, but it meant a lot.
“Iconic cases like these mean a little bit more. I don’t know if that’s right or wrong”, he said.
“It’s something I grew up with and I remember my parents speaking about this case.
“So, when many years later I was allocated the job of leading the re-investigation and help to bring it to a successful conclusion, it’s meant a lot.”
Was he concerned about the verdict? “The case itself I was confident about. As the trial rumbled on there were mixed views on how it was going and if we would get a positive result.
“I’m really pleased for the team who worked so hard for it and, more importantly, for Morag (Renee’s sister) and the wider family.”
Why did Bill MacDowell kill his son Andrew?
Being almost the same age as Andrew when the youngster was killed added to the poignancy.
“That’s the part that’s more difficult to comprehend. A three-year-old boy- why did that need to happen? That was always something we wrestled with.
“Clearly William MacDowell was in a situation where he felt he had to take the most drastic action possible.
“We formed the view he was probably in a position where he needed to eradicate that whole aspect of the double life he was leading at the time. It was really cold and calculating.”
DCI Geddes said the re-investigation focused on bringing Renee and Andrew’s killer to justice but also to find their bodies.
Following MacDowell’s conviction, police wrote to prison authorities seeking an interview with the killer.
However he died before the request could be followed up.
The team also “explored every avenue” to establish if anyone else knew information about the bodies.
“My belief is that only he knew where Renee and Andrew are”, said DCI Geddes.
“We had two of the team prepared to visit him if given any encouragement.
“But, from information from the prison service, it was clear to me he was never going to engage with us or reveal where he put those bodies.
Where are Renee and Andrew MacRae’s bodies?
“It remains for me an unresolved aspect of the case.
“While we were all delighted with the conviction, I know how Morag and the family feel about the fact this second aspect has never been resolved.
“So, the fact we have not achieved that hurts a little bit. That none of the team managed to get face-to-face with William MacDowell rankles a bit, even though I know deep down we wasn’t going to engage.
“But I feel like it’s unfinished business.”
A member of the investigation team continues to review evidence and look for other possible locations to search.
MacDowell’s family and friends have also been questioned again.
“While my belief is that no one else knows where they are, that can’t stop us at least trying and asking the questions of the people who are closest to him at the time and latterly in his life.”
Police received a number of calls during the trial and afterwards suggesting possible sites to look for the bodies.
Although no new information was provided, and no new searches are planned, it has been logged and added to the data being reviewed.
‘There is still hope’
It is hoped the TV programme may lead to fresh details being presented to police.
“Hopefully it will jog someone’s memory or prompt them to come forward and contact us. That will be very much appreciated.”
DCI Geddes said police are also liaising with contractors who will be working on sections of the A9 during future roadworks.
“Any avenue, any method we can explore to find out the unresolved aspect of where Renee and Andrew are – anything that can help – we’re totally up for and would buy into.
“At this moment in time there is nowhere else that warrants us carrying out any other search operation.”
But he said there is still hope: “Absolutely, you just never know. We all continue with hope that something will come that will get that final resolution for the family.”
Murder Trial: The Disappearance of Renee and Andrew MacRae is available to watch from August 22.
A preview can be seen here.