Kai Pennell, 35, stabbed Duane Keen, 47, at a flat in Blaenavon, South Wales in a jealous rage after bursting into his ex girlfriend’s flat just after the pair had sex
A man who killed a gifted boxer and MMA fighter in a jealous rage has been handed a life sentence behind bars. Duane Keen, 47, was found with severe injuries and declared dead at a property on Riverside Drive, Blaenavon, during the early hours of October 17 last year.
Kai Pennell, 35, admitted to the murder of Mr Keen who had a sexual relationship with Pennell’s pregnant ex, Rebecca Phillips. During a sentencing hearing at Cardiff Crown Court, Pennell was handed a life sentence with a minimum term of 23 years, reports Wales Online.
The court heard despite their relationship ending, Pennell had messaged Rebecca saying: “I f****** hate you but think the world of you at the same time… Like I’d do anything for you without question Becca Phillips, you know I idolise you… Night b****.”
In another, he messaged her: “I f****** hate you… You’re f****** foul, seriously what’s wrong with you.”
A further message said: “You are the best and the worst thing to happen to me, I’ve never loved and hated someone as much as I do you, I have never worried or cared about anyone like I do you, you make my heart melt and my blood boil at the same time like what the f*** have you done to my heart I want it back.
“I want to be able to switch off again and not feel anything but it’s impossible with you no matter how hard I try your my first thought in the morning and the last thing on my mind before I sleep no one has ever made an impact on me than you.”
In the lead up to the attack, Mr Keen was seen outside the Riverside Drive flats, speaking to Pennell through a window. Pennell could be heard saying: “You’re winding me up, you’re winding me up.”
He shouted “You’ve done this” and added: “Don’t do this now to me Rebecca. You’ll regret this.”
The defendant added: “Watch what’s going to happen.”
At 11.49pm, Pennell text Ms Phillips: “So would you rather me in prison than in baby’s life… What would you rather me be there and be a dad or gone for years, it’s your choice. Make the choice, I’m ready either way Becca.”
He started banging on Ms Phillips’ door, shouting for her to open the door and using a cupped hand to listen in. At 12.40am, Ms Phillips contacted Mr Keen and asked him to come over because of Pennell’s behaviour. Nine minutes later Mr Keen was seen walking to Riverside Drive.
CCTV from Pennell’s flat showed him reaching into a kitchen drawer, taking out an item with a black handle and putting it into his pocket.
Mr Rees said: “The prosecution case is that Kai Pennell has seen Duane Keen approaching Riverside Drive. He is selecting a knife for the premeditated attack on Duane Keen.”
Mr Keen arrived at the flats and was thrown a set of keys by Ms Phillips in order to let himself in.
He attended Ms Phillips’ flat and they spoke for 30 to 35 minutes about Pennell, and he told her to be “careful of him”.
They then went into the bedroom and had sex.
Describing what happened, the prosecution said: “After Duane Keen and Rebecca Phillips had finished having sex they heard the sound of the door unlocking. Rebecca Phillips then heard the sound of someone ‘booting the chain off’.
“Duane Keen got up and went to look. Kai Pennell came in to the property and pounced on him. Rebecca Phillips said they were grappling.
“Both men were stood up but it was as if Kai was over the top of Duane. She could hear moaning and groaning. She couldn’t see what was happening. She then heard Duane saying ‘He’s got a knife, he’s got a knife’.
He stabbed Mr Keen in the chest and told Rebecca Phillips:”‘You’re f****** next, you’re f****** next…You caused this’…You think I want to be like this? You’ve made me like this’.
Officers searched Pennell’s flat and found an open notebook with a picture of Pennell and Ms Phillips on a blood stained bed.
The notebook was open and said: “I literally can’t take it no more, Becca has mentally tortured me since being pregnant now to rub it in had got her ex again and said she’s going to f*** him and send me the video of her f****** and she has destroyed me.
“I can’t take no more I’m broken beyond repair, how can she do this to me? I’m so f****** heart broken I’m in a living hell.”
When he was arrested for murder, he kept repeating “sorry” and stated “I caught them in bed together. What kind of woman does that?”
Mrs Justice Stacey said: “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.”
Cardiff Crown Court heard Pennell was a former partner of Ms Phillips but she had ended their romantic involvement in September 2025.
Mr Keen was also a former partner of Ms Phillips although the pair had separated in May that year.
Christopher Rees KC, prosecuting, said: “The prosecution case is that (Pennell) remained obsessed with her and burning with jealousy.
“Kai Pennell was motivated by sexual jealousy to murder Duane Keen.”
On Tuesday, Mrs Justice Stacey sentenced Pennell to 23 years in prison and imposed an indefinite restraining order prohibiting him from contacting Ms Phillips.
She said: “In your twisted and self-piteous logic you told her 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.”
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.”
Mr Keen was described in court as being “well-known” in the mixed martial arts (MMA) community but “first and foremost a family man”.