A 37-year-old man has been sentenced for the brutal murder of his ex-wife in Cardiff. Thisara Weragalage was recently sentenced to 23 years of prison for killing his ex-wife Nirodha Niwunhella (32) by stabbing her eight times with a knife, before leaving her body hidden between two parked cars in a residential street in Riverside.
The sentencing took place at Cardiff Crown Court on Friday following a police investigation into the August 2025 attack. In what was noted as unusual development from Weragalage’s lawyer, Weragalage had pleaded guilty before the court in his first appearance never even trying to defend himself or offer an explanation.
The fatal incident in Riverside
The incident came to light after a resident of Riverside discovered Ms. Niwunhella’s bloody and anxiously trembling body with multiple stab wounds including to her ear lying between two cars at a parking space.
Upon discovering the body, the resident had immediately called in emergency services, who arrived at the scene around 7:50 AM, and declared her dead shortly after. A post-mortem examination later confirmed the cause of death as “multiple sharp force injuries.”
Forensic investigators spent several days at the crime scene to piece together the events leading to the fatal attack.
Case backdrop
As per information submitted to a UK court, the pair had married in Sri Lanka in 2017 before moving to Cardiff in September 2022 so Weragalage could better his career via higher education. However things had clearly changed as they started to live the immigrant life.
A neighbour told police they’d heard the pair arguing a lot through the walls and she repeatedly heard the name James, referring to Mr Stephenson.
The court heard how Ms Niwunhella, who worked at a care home – had become closer to Mr Stephenson, who was a colleague, and had confided in him about having problems with her marriage with Weragalage which led to Weragalage being jealous.
As per information submitted to the court, Weragalage became aware of the developing closer relationship between the two and told his wife he didn’t want her socialising with anyone he didn’t know. He also told her to go to work without a phone.
During the summer of 2023 Weragalage told a neighbour he was spying on his wife because he believed she was in a relationship with someone from work. In June 2024 Mr Stephenson told Ms Niwunhella they shouldn’t see each other anymore due to the actions of Weragalage.
Several months later, in April 2025, Ms Niwunhella and Weragalage moved into separate addresses and Ms Niwunhella told Mr Stephenson her relationship was over and they subsequently began their relationship.
Representing the family of the late Nirodha Niwunhella, state prosecutor MK Jones told the court that Weragalage “evidently struggled” with the break up and kept asking her to come back and even tried getting her dad to help change her mind.
Mr Jones read out a text message Weragalage sent to Mr Stephenson. “We moved to this country to make everything better but it’s all gone wrong,” it read.
Although Weragalage’s guilty plea spared the family a lengthy trial, the details of the attack remained central to the sentencing hearing. While the defense argued specific circumstances surrounding the relationship, the prosecution highlighted the premeditated nature of the violence.
Judges said the killing followed weeks of surveillance and preparation, describing it as a calculated act driven by control and obsession after the breakdown of the relationship.
Tracking routine before the attack
During the hearing, prosecutor Mr Jones told the court that CCTV footage from the residential car park near Mr Stephenson’s home — where Ms Niwunhella usually parked her vehicle — showed the accused visiting the location repeatedly in the days before the killing.
The footage captured him entering the car park on eight separate occasions, each time around 5.45am, indicating he had carefully studied her daily movements and schedule.
Photos recovered from phone
A later search of Weragalage’s mobile phone strengthened the prosecution’s case. Police recovered five photographs of Ms Niwunhella’s car dating back to May 2025.
Investigators said the images were taken at multiple locations, including: the residential parking area, outside her workplace and outside restaurants. Prosecutors said this demonstrated sustained surveillance rather than a sudden confrontation.
Knife bought a day earlier
The court was also shown CCTV footage from a B&M store in Pentwyn recorded the day before the murder. The footage showed Weragalage purchasing a three-pack of kitchen knives. Prosecutors confirmed that one of those knives was later used in the fatal attack outside Ms Niwunhella’s home.
According to the prosecution, the accused waited near her parked vehicle and attacked her when she approached. She suffered multiple stab wounds and died at the scene. The judge ruled the assault was premeditated and not an impulsive act, noting the combination of stalking behaviour, weapon purchase and repeated visits to the location.
The defence cited emotional distress following the separation. However, the court said the evidence clearly showed planning and intent. After the killing, the accused attempted to harm himself but survived and was later arrested.
He was subsequently convicted of murder and handed a jail sentence of 23 years and 9 months, with a minimum term to be served before parole eligibility.
Family and police response
The victim’s family described her as caring and deeply loved, saying the loss has permanently affected their lives. Authorities noted the case reflects a wider pattern seen in separation-related killings, where stalking behaviour escalates into violence.
Police stressed that repeated monitoring, threats and attempts to control a former partner should be treated as serious warning signs and reported early.