Alexander McCartney, from Newry in County Down, Northern Ireland, was identified as a dangerous online predator who targeted vulnerable children through social media platforms like Snapchat. His activities, spanning several years, involved catfishing—pretending to be someone else online—to deceive young girls into sending him indecent images, which he then used to blackmail them. This predatory behaviour culminated in tragic consequences, including the suicide of 17-year-old Cimarron Thomas from West Virginia, USA, in 2018, after McCartney blackmailed her with explicit images.
McCartney's criminal history began to surface in February 2016 when he was 17 years old and arrested by the Police Service of Northern Ireland (PSNI) after indecent images of children were discovered on his mobile phone. Despite being released on bail, significant delays in forensic examination of seized devices—due to under-resourcing in PSNI's cybercrime units—allowed him to continue his offending. Over the next two years, while on bail, McCartney engaged in abusive online communications with at least seven other children, tricking them into sharing explicit material and threatening to distribute it if they did not comply. For instance, in March 2018, information from the National Centre for Missing and Exploited Children (NCMEC) revealed he had coerced a girl in Lancashire, England, into sending an indecent image and was uploading child abuse material from his home IP address.
Further arrests followed: in March 2018, after additional tips from NCMEC about his interactions with a 14-year-old girl in Los Angeles who sent self-harm images; in 2019, linked to naked photos sent to a young person in Scotland; and again in July 2019, after evidence emerged of him receiving explicit videos from a 13-year-old in Florida and other children. Devices seized during these arrests, including phones, tablets, and computers, contained over 1,100 indecent images of children, along with evidence of his grooming and exploitation tactics. A Police Ombudsman investigation, commissioned in April 2021 by PSNI Chief Constable Simon Byrne, highlighted systemic failures: the investigating team was severely understaffed, with only five officers against a required 14, leading to backlogs in digital forensics. As Ombudsman chief executive Hugh Hume stated, 'This resulted in delays in the investigation and potential prosecution of those whose activities pose such a risk to children and young people, and opportunities to proactively follow evidence to identify where indecent images of children were being shared were missed.'
Despite these pressures, no individual officer misconduct was found, but the report criticised the PSNI's prioritisation processes, which favoured terrorism and serious crime over child protection cases. A National Crime Agency review in September 2021 echoed this, noting insufficient resources in the PSNI's Child Internet Protection Team (CIPT) to handle referrals timely, compromising victim safety. McCartney, who was studying Computer Science at college during some of his offending, exploited his technical knowledge to perpetrate these crimes from his bedroom.
In October 2024, at Belfast Crown Court, McCartney was convicted of multiple serious offences, including unlawful act manslaughter in connection with Cimarron Thomas's death, inciting children to engage in sexual activity, and making and possessing indecent images of children. He was sentenced to a minimum of 20 years' imprisonment, reflecting the severity of his actions that spanned international victims and caused profound harm. Cimarron's father, Benjamin Jay Thomas, also took his own life in January 2020, underscoring the ripple effects of McCartney's predation. The case has prompted calls for better resourcing in digital forensics to protect children from online threats, as Hume emphasised: 'McCartney’s targeting of young girls is a clear example of violence against women and girls in the digital space... it can have devastating consequences and should carry equal weight in terms of the prioritisation of digital forensic examinations.'