The motive for the murder of an Aberdeen grandmother remains unclear, the senior detective who put her dangerous killer behind bars said today.
Prolific violent offender Norman Duncan, 43, killed Margaret Robertson in a drug-fuelled attack at her flat and was yesterday jailed for at least 20 years.
Following his conviction for the September 25 2019 murder, it was revealed Duncan had 74 convictions prior to the deadly drug-fuelled knife attack in Promenade Court.
The man leading the murder inquiry, Detective Inspector Gary Winter, today told the Press and Journal that he had already encountered Duncan during the course of his career.
“His previous convictions sheet is pretty extensive – significant enough offending to result in a large volume of prison sentences over the years,” the Det Insp said.
Margaret’s children Michelle and Mark, issued a statement following the verdict: “We still have unanswered questions as to why it happened at all.”
They asked Police Scotland’s Major Investigation Team to get justice for their much-loved mum, daughter and grandmother – and to explain why she was killed.
Unfortunately, the final question may never be answered, Det Insp Winter said.
“We don’t have that account from Norman Duncan as to why it happened,” he said.
“Norman Duncan knows why and he’s chosen in his interview not to tell us and he’s chosen when he gave evidence not to cover that.”
During the murder trial, Duncan heard the wealth of overwhelming evidence against him.
It included traces of his blood and DNA at the crime scene and CCTV footage showing him changing his clothes on the day of the murder.
Murder ‘probably’ sexually motivated
Det Insp Winter said that he believes 54-year-old Margaret’s murder was “probably” sexually motivated.
“The circumstances of a woman being found naked in her bed with the DNA of the accused present on her and injuries to her private parts, which are unexplained. Is it a quantum leap to suspect that that is sexually motivated or happened at the time of a rape?
“It’s probably the most likely scenario, but that’s not what we heard from Norman Duncan.”
And the question of why Duncan came to meet Margaret and how he ended up in her flat is another mystery that won’t be answered unless the killer confesses.
It’s known that Duncan was going back and forth to buy crack cocaine at the block of flats where Margaret lived, but the exact circumstances of their fateful meeting are not known.
‘A level of justice’
Det Insp Winter said: “His association with the deceased is relatively unknown.
“He’d certainly not gone to (Margaret’s) address to source crack cocaine. Other witnesses spoke to them being the supply of the crack cocaine in other flats within the block.”
The Senior Investigating Officer said his investigation had secured “a level of justice” for Margaret’s family.
In a statement, Michelle and Mark said Duncan “has taken so much from us and impacted on our lives in many ways”.
“It is hard to comprehend our mum has been taken from us and she is in our thoughts every day and we hope she can finally rest in peace,” they said.
