A domestic abuser who murdered his ex-partner and her new boyfriend should have his whole life sentence reduced as it is “not necessary”, the Court of Appeal has been told.

Marcus Osborne was jailed in March for the double killing which left Katie Higton, 27, with 99 injuries; and Steven Harnett, 25, with 24 wounds including mutilated genitals; after which Osborne said: “Romeo and Juliet can die together now.”

Leeds Crown Court heard that Osborne, 35, lay in wait for Ms Higton and attacked her as she entered the house they once shared in Huddersfield, West Yorkshire, in the early hours of May 15 last year.

He then used Ms Higton’s phone to pretend to be her to lure Mr Harnett to the house before killing him while four children were inside, going on to rape another woman at knifepoint.

Osborne is seeking to challenge his sentence, with his lawyers telling the Court of Appeal on Wednesday that he should have been sentenced to life with a “very long minimum term”, rather than receiving a whole life order.

John Elvidge KC said: “We invite this court to consider looking at the case overall, particularly having regard to his guilty plea.

“This is a case where the last resort option was not necessary and he could have been given a very long minimum term.”

Osborne attended the hearing via a video link from HMP Wakefield, wearing a grey Adidas jumper.

Steven Harnett and Katie Higton (West Yorkshire Police/PA)
Steven Harnett and Katie Higton (West Yorkshire Police/PA)

His sentencing hearing was told that Ms Higton had been in a relationship with him for five years, but left him in early May last year after an assault which was “the last straw”.

Ms Higton had complained to police that the relationship was “coercive, controlling and physically abusive” in the last two years and that she had been regularly assaulted, including one incident when he threw a cat at her.

In the days before the murders, she also told West Yorkshire Police that Osborne had told her “he would slit her throat if she said what he had done”, and that “if she ever got a boyfriend he would kill them both”.

Osborne was arrested on suspicion of domestic violence offences on May 12 last year and bailed with conditions not to go back to their home, but spied on Ms Higton over the following days and found out about the developing relationship between her and Mr Harnett by hacking into her Snapchat account.

He later admitted two counts of murder and single counts of rape and false imprisonment.

The sentencing judge, Mrs Justice Lambert, said that Osborne was heard saying: “I warned you I was going to kill you … this is your fault this is happening”, and was described as washing himself between killings, laughing and jeering.

He later invited a neighbour into the living room to see the bodies, which the judge said was “as if you were proud of what you had done”.

She said that the crimes were “horrific” and that “even a very long minimum term would not amount to just punishment”.

But Mr Elvidge told the hearing in London that Osborne’s guilty pleas should have been given “heavy weight” as they spared the rape victim from having to give evidence.

He said: “The court should be slow to deny any credit for a guilty plea where that plea has not only saved public time and money … but also spared someone who is both a victim and a witness from having to give evidence about highly traumatic events.”

He continued: “The effect of passing a whole life term in this case is that the applicant’s guilty pleas to all of these charges carry no value.

“His decision to spare her the further ordeal, reliving the whole experience of that night, is to all practical effect unrecognised. That, we submit, is not right.”

Jonathan Sandiford KC, for the Crown Prosecution Service, said that Mrs Justice Lambert “adopted the right approach” and that the appeal bid should be dismissed.

The Lady Chief Justice Baroness Carr, Lord Justice Jeremy Baker and Mr Justice Bennathan will give their judgment later, with Baroness Carr describing the case as “extraordinary” and “unbelievably tragic”.