Darren Pencille has been jailed for life for murdering a man he stabbed repeatedly during a confrontation on a London-bound train, while his girlfriend Chelsea Mitchell was also jailed for assisting an offender.
The prosecution at his trial painted a picture of a man with a history of mental health issues but also of violence – Pencille had been convicted of an earlier knife attack that bore striking similarities to the killing of Lee Pomeroy.
The 36-year-old defendant relied upon his girlfriend in court as much as he did on the day he stabbed Mr Pomeroy 18 times and left him to die.
Pencille chose not to take the stand and speak in his defence, leaving it to Mitchell to give an account of their lives and their actions that day and to describe their co-dependent relationship.
The court heard how Pencille could not deal with crowded places – shops, supermarkets, railway stations, trains and hospitals.
Whenever panic struck during a rail journey, “nine times out of 10” he would call Mitchell, who has borderline learning disabilities and whose IQ is ranked in the lowest 1% of the population.
Mitchell, 28, would talk to Pencille – who she called Jimmy – to calm him down and collect him if he had been unable to stay on a train. She would either take him to her flat in Farnham, Surrey, where they lived together, or to a quieter railway station or on to his destination.
She would do his shopping, sending him WhatsApp images of the items she had bought to make sure they were the right ones.
Neither of them had dealt with the loss of their stillborn son, Romeo, who died the previous summer, the Old Bailey heard during the trial.
Mitchell, who met Pencille on a dating website, told jurors their feelings were still raw and the pair had been struggling – the court heard the defendant carried a 20-week ultrasound scan of Romeo in his wallet.
She said Pencille had supported her when depression after the stillbirth left her unable to get out of bed and she still had to care for her young daughter, who called Pencille “Daddy”.
When she was questioned in court about why, on the day of the killing, it apparently took her more than nine hours to work out what her boyfriend had done, Mitchell said: “I’m a bit slow.”
“If someone tells a joke, I don’t pick up on it until five minutes later,” she explained.
In the hours after the killing, as Mr Pomeroy’s teenage son and other traumatised passengers were supported by the police, on-the-run Pencille had called Mitchell to collect him and take him to their Farnham home, about 15 miles from the scene of the stabbing.
He discarded clothing and took a shower.
While police combed the area around Clandon for the killer, Pencille suggested to Mitchell they visit Frensham Ponds to let off lanterns in memory of Romeo.
The beauty spot was where they would go to find peace and quiet and “gather their thoughts”, the young mother told the court.
“It was quite emotional over Christmas,” she said. “We didn’t have our son.”
After their trip to the ponds the pair headed to the Sussex coastal town of Bognor where Pencille had a flat. Mitchell gave her daughter dinner and watched EastEnders.
Later that night they returned to her flat in Farnham, where the pair would be arrested early the next day.
By this point, police knew their prime suspect had used a knife in anger before. In 2010, Pencille admitted wounding with intent to cause grievous bodily harm in relation to an attack on his 24-year-old housemate – although Mitchell said her boyfriend had never revealed his violent past to her.
Pencille had gone into his victim’s bedroom to borrow cigarette papers but became loud and aggressive and, after a disagreement, followed his housemate out of the room.
Seconds later, after hearing shouting, a witness followed them and saw the man bleeding heavily from his neck – his life-threatening injuries included two stab wounds to the neck and one to the shoulder.
During his murder trial, the jury heard that Pencille claimed to be “hearing voices” during his confrontation with Mr Pomeroy.
It transpired that in the months before the killing, he had not been taking his medication.
Various drugs had been prescribed to treat his anxiety, depression and psychotic conditions including schizophrenia. These included diazepam, mirtazapine and olanzapine, but none of those substances was found in his urine sample after the killing, a forensic scientist said.
Jurors heard that Mr Pomeroy followed Pencille through the train’s carriages as the pair taunted one another, leaving the killer with nowhere to go and no way to get off the moving train.
Mr Pomeroy’s son described how his father would never start a fight, but also would never “not reply”.
However, his father’s killer had boarded the train carrying a knife and, in the attack that followed, Pencille stabbed Mr Pomeroy 18 times in 25 seconds. He severed the 51-year-old’s jugular vein and carotid artery, leaving him rapidly bleeding to death.
Pencille’s unrelenting assault left Mr Pomeroy with a wound to his neck, eight to his torso and others to his arm, his hands and his thigh. He bled so profusely the blood covered his clothing, the area of the train where the attack happened – and Pencille’s own clothes.
Mr Pomeroy’s family told the BBC in March how the murder had left them not only heartbroken but also terrified.
His sister Kim Pomeroy said: “If this can happen to a 51-year-old man going about his business on a train in the middle of the day, this terrifies me, because if it can happen to him, it can happen to anybody.”
She said the family had lost a loving father, husband, son and brother, a generous man who cared about people.
“We are absolutely heartbroken. Our family has been destroyed,” she said.
Mitchell told the court it was many hours after the attack that she realised what her boyfriend had done, only discovering a man had been stabbed and a killer was on the run after she had put her daughter to bed.
The 28-year-old said it was at this point that she looked at the day’s news coverage on her phone.
During the trial, Mitchell was reprimanded for sending a Father’s Day card and letter to Pencille in Belmarsh Prison – her bail conditions had barred any contact.
In the letter, Mitchell urged Pencille to “stay strong” and “keep fighting”.
She wrote: “I miss you so much, everything is falling apart. Loosing [sic] everyone I love and all I want us [sic] my family back… Finding everything so hard. All I want is you by my side.”