THE family of a much loved MMA fighter has told Cardiff Crown Court his killer was a coward who had shown no remorse after murdering 47 years old Duane Keen in a fit of sexual jealousy

Kai Pennell, aged 25 of Blaenavon was told he would serve at least 22 years in jail for stabbing Mr Keen at the Blaenavon home of Rebecca Phillips - a woman they had both been romantically involved with.

Throughout an emotional impact statement delivered by Mr Keen’s son Joshua, Pennell, also of Blaenavon, grinned and sneered in the dock, with Mr Keen calling for him to remain in prison for the rest of his life.

“Sons shouldn’t be burying their father as a result of another,” he said.

“You showed no remorse and completely disrespected my dad’s life. You’ve showed no remorse shown throughout this process.”

“You signed your own life away to a lifetime of loneliness.

“I can only pray he gets the maximum sentence.”

Mr Keen described his father as being a ‘best mate’ to his sons, and a caring grandfather.

"He was our protector - there was nothing he wouldn't do for us," he said.

The court heard the murder came about as a result of a relationship with Rebecca Phillips who had split up with Keen in May 2025, before starting a relationship with Pennell which ended in September 2025.

Despite the split, Pennell remained ‘obsessed’ with Phillips and grew increasingly jealous of Keen with messages and phone calls between the pair becoming increasingly demanding and controlling.

"You make my heart melt and my blood boil at the same time," Pennell wrote in one message while another said "What have you done to my heart, I want it back.”

On the night of October, 17 2025, Pennell had bombarded Phillips with ‘disturbing’ calls and text messages, accusing her of seeing other men, which prosecutor Christopher Rees KC told the court showed Pennell was ‘obsessed with Phillips and burning with jealousy’.

Feeling she was at risk she asked Keen to come to her home, where they were both ambushed by Pennell.

CCTV footage showed Pennell outside the flats, peering through the spy hole in the front door. He was initially see to be brandishing a small kitchen knife before re-appearing with a large kitchen knife, around 8 to 9 inches long.

Mrs Justice Stacey said, “I am sure you went back to your flat to get a bigger knife in order to kill Duane, not just cause him really serious harm. This was not a spontaneous attack and it was unprovoked.”

Phillips told police she and Keen were in bed when they heard someone fiddling with the lock and ‘booting the chain off the door’.

She said Pennell pounced on Keen and both men began grappling.

When she returned to the flat after running to fetch a neighbour to help, she said she found ‘blood all over the walls’.

"Kai was like a demon had taken over his body," she said. "His face was petrifying.”

Pennell fled the scene and was found by police helicopters in a wooded area close to the flats a few hours later.

A post-mortem recorded a number of stab wounds to Keen's body, as well as slash wounds on his arms where he had tried to protect himself. When interviewed by police about the attack, Pennell answered ‘no comment’.

Toxicology reports found no alcohol in his system but levels of heroin, cocaine and methadone were detected, likely to have been from use over the previous 24 hours although the court heard it was "not possible" to know what impact the drugs may have had on Pennell, who was a long-term drug user.

Defending, David Elias KC said only a life sentence was possible, but Pennell's guilty plea meant the family and witnesses had been spared the ordeal of a trial.

He said Pennell had been diagnosed with ADHD at about the age of ten, and had suffered mental health problems and had been sectioned in 2023.

The court was told Pennell had previous convictions, but no details were given to the court - although the judge referred to them as minor.

Sentencing Pennell to a life imprisonment, with a minimum term of 22 years and 238 days in jail, Mrs Justice Stacey said his behaviour had been volatile on the day of the attack, noting he was ‘spiralling out of control’.

“You appeared unable to accept that she did not want to be in a relationship with you. You would not leave her alone and you became fixated on whether she was seeing anyone else, including her ex, Duane Keen.”

She said: "In your twisted and self-piteous logic, you told Phillips that your murder of Duane was somehow her fault.

"The only person to blame for Duane's murder is you.

"You were motivated by sexual jealousy and anger when you killed Duane, and as a way to try and control and punish Rebecca for breaking up with you and remaining friends with Duane."

She said other charges relating to threats to kill Phillips would remain on file, and imposed an indefinite restraining order prohibiting Pennell from contacting his ex-partner.

In a statement, his family said: “Although justice has been given, the life sentence will never be truly enough, as we the family have lost our loved one who will never have his life to live and we now have to live the rest of our lives without him.

“We the family would like to thank the police, CPS and all the team that have worked tirelessly on this case and have supported us throughout the past several months.”

Detective Chief Inspector Jitka Tomkova-Griffiths, of Gwent Police, said: “Kai Pennell killed Duane Keen in a jealousy-fuelled and violent attack.

“Taking a knife from his own property implied that he intended to cause serious harm when confronting Duane in the early hours of that morning.

“His actions had devastating consequences and Duane’s death has impacted the lives of his family, loved ones, friends and community.

“I’d like to pay tribute to the friends and family who have had to come to terms with Duane’s death and shown great strength throughout this difficult process.

“I know today’s sentencing will never bring him back. However, I hope this outcome brings some consolation and closure for them.”