THE family of a mother murdered by her violent boyfriend have been given permission to proceed in a bid to expose alleged “police failings”.

Susan Nicholson, 52, was murdered by her boyfriend Robert Trigg in 2011 – five years after he killed another lover, 35-year-old Caroline Devlin.

Neither death was originally treated as suspicious by police and an inquest into Susan’s death initially sited as “natural causes” – until her family hired investigators who proved she had been murdered.

Trigg, 51, who claimed he found her dead on the sofa, was subsequently convicted of her murder – and the manslaughter of ex-girlfriend Caroline in 2006.

An independent police inquiry revealed Susan was visited by Sussex Police six times before her death and the family think the force should have done more to protect her.

The family has now been granted permission by the court to proceed with a crowdfunded legal bid for a full inquest into her death to probe alleged police failings. The two-day hearing is listed at the Queen’s Bench Division of the High Court next month, after the family crowdfunded £3,000.

But jailed Trigg, who was sentenced to 25 years, has argued the police did their job properly and the challenge should be dismissed, the family’s lawyers claim.

Sussex Police have also argued the judicial review should be dismissed and indicated they will claim legal costs from Susan’s parents should the force win, the lawyers claim.

Susan’s dad Peter Skelton, of Worthing, said: “I do not believe Sussex Police did enough to protect Susan.

“They had all the information about Trigg’s history of violence against Susan and other women. They knew Caroline had died while in bed with him. Even after Susan’s neighbour called the police and they found Susan with injuries to her face, they didn’t see that he was a danger to her.

“We want to ask the officers what they did to protect Susan, and we had hoped that Sussex Police would want that, to ensure that their officers are alert to the dangers faced by victims of domestic violence and protecting them properly. We are hurt and disappointed that they have chosen to fight our challenge instead and that they want us to pay their legal costs if we lose.”

Susan’s parents Peter and Elizabeth Skelton, who are both in their eighties, have years arguing Sussex Police should have realised her life was in danger.

Trigg had a well-documented history of domestic violence towards at least three previous partners, which was made available to police, a pre-inquest review heard.

Sussex Police initially failed to treat the two deaths as suspicious until Ms Nicholson’s family found more evidence.

Lewes Crown Court heard it was only after Ms Nicholson’s parents hired professionals to re-examine the original pathologist’s report that the case went to court.

Trigg was eventually convicted and sentenced to 25 years in prison without parole in 2017 for Susan’s murder and for the manslaughter of Caroline.

An independent police inquiry identified “missed opportunities” in the original probe by Sussex Police.

At least two officers were involved in the investigations into both killings.

The West Sussex Senior Coroner had ruled there would only be a short inquest into Susan’s death.

But Susan’s parents want a full ‘Article 2’ inquest to look at whether the police could have prevented Susan’s death.

The Royal Courts of Justice have granted permission for a judicial review in March, to decide whether a full inquest can take place.

Susan’s son Joe, 32, said: “Trigg would have killed again and again if my grandparents hadn’t fought so hard for Sussex Police to take my mum’s death seriously. “It’s because of them that he is in prison now. It’s really upsetting that Sussex Police are now fighting to prevent a full inquest into whether they did enough to protect my mother from Trigg.

“They should be wanting to ensure that they are doing all they can to protect victims of domestic violence like my mother and Caroline Devlin from being killed by their parents. “My grandparents are in their eighties. They won’t give up until they know they’ve done what they can for my mother. “I am very worried that Sussex Police will send them a big bill for their legal costs if they lose this challenge.”

A spokesman for Sussex Police said: “This matter will be the subject of Judicial Review and we are therefore not in a position to comment at this time.”