In January, Simon Vickers was found guilty of murdering his 14-year-old daughter Scarlett after a jury rejected his claim he had killed her in a play-fight. His partner, Scarlett’s mother, is adamant it was an accident.

It’s the question Sarah Hall will hear for the rest of her life – how can she possibly support the man who was convicted of murdering her daughter?

“I know he’d never harm Scarlett,” she insists.

Ms Hall claims 5 July had been a normal Friday night at the family’s Darlington home.

She says the close-knit trio, who dubbed themselves the Three S’s, called them “happy Fridays” as it meant another week of work and school was over.

Scarlett ate her dinner and spent the evening in her bedroom, chatting with friends and playing games online.

Her parents drank wine and watched the men’s European Football Championships on TV in the living room.

Vickers also smoked some cannabis, something he regularly did to ease backache caused by his manual job in a factory, Ms Hall says.

At about 22:00 BST, the teenager joined her parents in their small kitchen where her mother was putting the finishing touches to the adults’ tea, spaghetti bolognese and garlic bread.

Ms Hall becomes very emotional when she describes what happened next.

She and her daughter were throwing grapes into each other’s mouths, she says, having “just a fun fight”.

Vickers also joined in. As Ms Hall was busy draining off the pasta in the sink, her partner of 27 years and their daughter were “mucking about by the back door”.

Precisely what happened next is still the source of much confusion for her, but she is certain it was not criminal.

During the play-fight, Ms Hall says she accidentally nipped Vickers with the kitchen tongs.

He reacted and Scarlett “jokingly” called him a wimp, Ms Hall says.

Vickers replied “how would you like it” and swiped the tongs across the worktop towards his daughter, Ms Hall says.

A kitchen knife had been placed next to the tongs, ready to cut the garlic bread, and Ms Hall believes the utensil caught the knife and wedged it against a granite chopping board, leaving the blade protruding out from the bench.

At that same moment, Scarlett moved towards her dad, perhaps in a bid to grab the tongs, and ran on to the blade, Ms Hall says.

During Vickers’ trial, he also claimed the injury was inflicted accidentally, but a pathologist said it was “practically impossible” for it to have been caused by anything other than a knife being held firmly in a hand.

Vickers initially said he hurled a knife instead of what he thought was a spatula, but also told paramedics and police at the scene Scarlett had “lunged” towards him and the blade “just went in”.

Sentencing Vickers, judge Mr Justice Cotter said he had “no doubt” Scarlett’s father had been holding the knife.

What Ms Hall knows for sure is her daughter cried “ow”, then blood started to pour from her side.

“I just thought ‘that’s not right, there’s something seriously wrong’,” Ms Hall says.

Ms Hall grabbed a tea towel to try and stem the bleeding, her daughter collapsing to the floor.

Vickers took over from her and shouted at Ms Hall to call 999.

It took the ambulance what “felt like forever” to come, but paramedics were actually there within minutes and immediately started trying to save Scarlett’s life.

Their efforts were in vain.

Scarlett died from a single 4in-deep (11cm) stab wound to her chest.

The blade needed only mild force to pass between her ribs and into her heart, causing catastrophic bleeding, a pathologist would later say.

The police arrived and Ms Hall and Vickers were arrested for attempted murder and taken to separate police stations.

When Ms Hall was given the news her daughter had died, she cried: “No, no, please no. My little girl.”

She was given a sedative and put into a cell where she remembers waking up intermittently, crying, before lapsing back into her medicated sleep.

Scarlett was the girl who had always made her parents laugh.

She was bursting with energy, beautiful, boisterous and sassy, her mother says.

“She was an incredible girl and she was becoming an incredible young woman.”

Both Ms Hall and Vickers were initially charged with murdering their daughter, but the case against her was quickly dropped and Vickers alone stood trial at Teesside Crown Court in January.

The strongest evidence against him was from pathologist Dr Jennifer Bolton, who concluded the knife must have been being firmly held in a hand to cause the injuries it did.

After a 10-day trial, during which Ms Hall gave evidence in support of Vickers, and about 13 hours of deliberation, jurors found him guilty of murder with a 10 to two majority.

Vickers could have pleaded guilty to the lesser charge of manslaughter but Ms Hall says he said he needed “to stand up in court and tell them that he would never, ever harm” Scarlett.

Jailing him for life with a minimum prison term of 15 years, Mr Justice Cotter said a “momentary but devastating act of anger” had robbed Scarlett of her life, adding Vickers’ account of it being a “freak accident” was “unconvincing and wholly implausible”.

Ms Hall says that is “absurd”, adding her partner “never had a flash of anger”.

“I was there that night,” she says. “There were no arguments. There was no temper, no shouting.”

She says she was shocked when the verdict was announced, adding: “I thought I’d misheard.

“It’s just been a never-ending nightmare.”

Responding to social media speculation in the aftermath of the trial that Vickers must have been a controlling and abusive partner, Ms Hall said: “No, never.

“He was understanding, comforting.

“[Our relationship] was very supportive, never controlling.”

Ms Hall says her family was a happy one and they “did everything together”.

Vickers and Scarlett had a very loving relationship, Ms Hall says, adding they were “as daft as each other”.

When challenged about how she can stay with Vickers, Ms Hall says she is still resolutely supporting him.

“How can I blame him for an accident when I know he’s in as much pain as I am?” she says.

“If I thought he’d done it deliberately then no, I wouldn’t have been here [doing this interview].

“I would have protected her with my life, as would he.”

At Vickers’ sentencing, the court heard Ms Hall’s and Vickers’ parents remained “resolute in their belief” he “did not intend Scarlett any harm”.

Ms Hall dreams about her daughter every night, remembering with horror each morning that she’s really gone.

“I just want her back so much,” she says. “I’m not sleeping well, I’m not eating well. I’m just existing.”

She has only been back to their home on Geneva Road three times since Scarlett’s death.

The semi-detached house is now just a “shell” because “they’re not here”, she says.

“It was a happy house,” she says. “I see the memories everywhere.

“Even going back into [Scarlett’s] bedroom, she left a blazer there with all her school stuff still in.

“Everything was just left how it was.”

Vickers’ sentence is set to be reviewed by the Court of Appeal, after Solicitor General Lucy Rigby KC said she thought it was too lenient.

A list of organisations in the UK offering support and information with some of the issues in this story is available at BBC Action Line

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