Jurors found that Sussex Police did not take reasonable measures to avoid harm coming to Ms Nicholson, despite the fact that they knew or ought reasonably to have known there was a ‘real and immediate risk’ to her life.
In a statement after the inquest, her parents said they were ‘pleased and relieved’ at the jury’s conclusions, adding they had felt ‘ignored and spoken down to’ by police.
The 52-year-old was murdered by Trigg in 2011, five years after he had killed his previous partner, Caroline Devlin.
Both women were killed at their homes in Worthing, five years apart, but neither death was initially deemed suspicious by Sussex Police.
The coroner at the original inquest found Ms Nicholson’s death to be accidental.
After Trigg was found guilty of killing the two women, the High Court overturned the original inquest into Ms Nicholson’s death and ordered a new one be carried out.
At the inquest on Monday, jurors in Crawley read out their answers to a number of questions in relation to Ms Nicholson’s death, including possible failings by Sussex Police.
This included what police knew at the time and whether a lack of action contributed to her death at the hands of Trigg.
Ms Nicholson’s parents, Peter and Elizabeth Skelton – who have campaigned for a decade for their daughter’s death to be adequately investigated – were in court to hear the verdicts.
The jury concluded that Sussex Police knew or ought reasonably to have known that Trigg posed a real and immediate risk to Ms Nicholson’s life.
They also found that the force did not take such measures as could reasonably be expected of them and that this caused or contributed to Ms Nicholson’s death.
Jurors also found that the decision to declare the death of Ms Devlin unexplained, and/or not to launch a homicide investigation, was a significant failure.
They said there was a ‘realistic possibility’ that Ms Nicholson’s death may have been prevented if Ms Devlin’s death had been declared and investigated as suspicious.
The jury was also asked whether the decision by the pathologist (instructed by the coroner) not to refer the death of Ms Devlin to a Home Office forensic pathologist, when they were unable to find the site of any ruptured aneurysm, was a significant failure, and if this caused or contributed to the death of Ms Nicholson.
They found that it was a significant failure and that it did cause or contribute to her death.
In a statement after the inquest, Mr and Mrs Skelton said: “This inquest has explored the failures of the police to protect Susan and to adequately investigate Caroline Devlin’s death.
“We are pleased and relieved that the jury have recognised what seemed apparent to us; that the police did not do enough to protect Susan, nor did they do enough to investigate Caroline’s death.
“It took six years for Trigg to be prosecuted for the murder of our daughter Susan, and the manslaughter of Caroline.
“Throughout this time, during which we were mostly acting alone without legal representation, we tried again and again to persuade Sussex Police to properly investigate Susan’s death.
“We were ignored and spoken down to. We were treated like a nuisance and it was implied that we were lying or obsessive.
“Instead of enjoying our retirement years, we have suffered mental torture for over a decade fighting to get justice for Susan.
“Our efforts over the 10 years since Susan’s death have not made this process or this outcome any less distressing.
“We hope that Sussex Police will reflect on all the jury’s conclusions, and ensure that victims of domestic violence, and their families, are better treated in future.”