**Convicted Cardiff Sex Offender Dies Behind Bars Following Sentence for Assaulting Vulnerable Teen**
A convicted sex offender, Thomas Mullen, who assaulted a teenager in a harrowing case that shocked the local community, has passed away in prison while serving his sentence. Mullen, aged 79 at the time of his death, had been serving a 12-year term following a conviction for multiple sexual offences against a vulnerable young woman whom he encountered whilst she was alone in a Cardiff underpass.
Mullen’s death was confirmed on 3 May 2025 at Parc Prison in Bridgend, where he had been held since his conviction in 2018. Prison authorities have publicly stated that an investigation into the circumstances surrounding his death is ongoing, which is standard procedure in such cases. The Prisons and Probation Ombudsman will be overseeing the review to ensure transparency and any relevant findings are made available in due course.
The disturbing offence occurred just days before Christmas in 2017. Mullen, described during his trial as a grandfather from Cardiff, was walking his dog when he noticed the teenager, who was evidently vulnerable, sitting alone in an underpass. Prosecutors told Cardiff Crown Court that Mullen approached the girl under the guise of kindness, offering her a hot drink and inviting her back to his home in Llanedeyrn.
Once at his flat in Lincoln Court, Mullen locked the door and subjected the girl to what was described in court as a “frightening” and distressing ordeal. During the trial, the jury heard that he attempted to justify his actions by suggesting the teenager had encouraged his advances, remarks the court found to be part of a calculated attempt to evade responsibility. Among his claims was the assertion that the victim had “licked her lips”, but these desperate bids to blame the victim were firmly rejected by the jury, who found him guilty of sexual assault by penetration and two counts of sexual assault.
The impact of the assault upon the young woman was described as severe and long-lasting. The teenager’s victim personal statement, read in court, detailed the profound psychological harm she suffered as a result of Mullen’s actions. Reports indicated that she struggled deeply with her wellbeing, at one stage considering suicide and making radical changes to her appearance in an effort to cope with the trauma.
In addition to the act itself, the court heard that Mullen tried to intimidate the victim into silence, warning her not to tell anyone what had happened and instructing her to deny everything if questioned by the police. This aspect of the case drew further ire from the presiding judge, who highlighted the calculated nature of his abuse.
Mullen’s defence, led by barrister John Ryan, painted a picture of an individual whose life had been marked by loss and personal difficulty. The court was told that Mullen had become increasingly isolated following the death of his partner from breast cancer in 2006 and had long struggled with alcohol dependency since the turn of the millennium. However, these mitigating factors were ultimately deemed insufficient to outweigh the gravity of his crimes.
Passing sentence, Judge Tracey Lloyd-Clarke underlined the serious and irreversible effects of Mullen’s actions. She remarked on the extreme vulnerability of the young woman, emphasising that Mullen would have recognised her distress and isolation when he encountered her in the underpass. The judge described his return to the scene and subsequent targeting of the teenager as a deliberate and predatory act, further aggravating the seriousness of the offence.
With his death occurring before the completion of his sentence, questions may be raised about justice and closure for the victim and her supporters. The ombudsman’s investigation is expected to provide further clarity on the circumstances of his passing, but it will not alter the long shadow cast by his actions on those affected.
Mullen’s case serves as a stark reminder of the lasting impact of sexual violence, particularly when committed against the vulnerable. As the community comes to terms with the conclusion of this tragic chapter, attention remains focused on supporting survivors and ensuring rigorous systems of accountability within both society and the criminal justice system.