Shrewsbury love triangle killer who knifed young dad through the heart is jailed for more than six years

Ex-soldier Kai Sainz-Stafford, 24, pleaded guilty to the manslaughter of Shrewsbury carpenter Sam Siviter at Stafford Crown Court yesterday (Monday, November 10, 2025) after his murder trial was brought to an abrupt conclusion.

Sainz-Stafford was back in the dock today to receive his punishment for killing 35-year-old Mr Siviter - and for stabbing another man in September last year. He was under investigation for that offence when he knifed Mr Siviter to death.

He bowed his head during parts of the hearing, dressed smartly in a light blue shirt and a navy tie as Judge Sylvia de Bertodano informed him of his fate. Family members of both Sainz-Stafford and Mr Siviter filled the public gallery. Three members of the jury also returned to their seats to see the outcome of the case.

The murder trial jury heard that Sainz-Stafford and Hannah Cottrell - Mr Siviter’s ex - had been sharing “flirty” text messages for around a fortnight in the build up to the fateful night of the incident, Thursday, May 1 this year.

Ms Cottrell, who the jury was told had been drinking since before 6pm, paid for a taxi for Sainz-Stafford to go to her house in Lambourn Drive, Bicton Heath, Shrewsbury late at night to meet for the first time.

Her children were upstairs in bed and Glynis Taylor, the mother of her ex Sam Siviter, was in the kitchen.

Mrs Taylor was on good terms with Ms Cottrell, who had one child with Mr Siviter and another from a previous relationship. She would go to the house to help with childcare.

Meanwhile Mr Siviter, who was banned by social services from attending Ms Cottrell’s home after fighting in the street with a man he thought she was seeing, was living with a neighbour in a house which backed onto Ms Cottrell’s. He even built a gate so he could go directly through his back garden to Ms Cottrell’s.

The jury was told that Mr Siviter and Ms Cottrell “liked to wind each other up”, and that the root cause of many of their rows would be when one of them thought the other was seeing someone else.

Sainz-Stafford’s taxi arrived at Lambourn Drive at 11.17pm. He told the driver he was “going to have some fun with a girl”, and he later told police that they kissed.

Mrs Taylor, who was “massively drunk” according to Sainz-Stafford, phoned her son a short time later at 11.42pm in a 21-second call. She made two more calls a minute later which went unanswered.

At 11.47pm, a neighbour in Lambourn Drive phoned an ambulance after Mr Siviter collapsed outside. He had been knifed three times - once in the leg, once in the knee and once through the heart.

He died in the back of an ambulance minutes later at 12.33am on Friday, May 2. The fatal wound was 7cm, and penetrated through his skin, muscle, cartilage and into his heart.

Mr Siviter was born and grew up in the West Midlands and supported West Bromwich Albion. He moved to Shrewsbury as a 13-year-old.