Mahmood Hussein Mattan was born in British Somaliland in 1923 and his job as a merchant seaman took him to Wales where he found work at a foundry in Tiger Bay. In Cardiff he met Laura Williams, a worker at a paper factory. The couple married just three months after meeting, but as a multiracial couple they suffered racist abuse from the community. The couple had three children, but in 1950 they separated and afterwards lived in separate houses in the same street. In 1952 Mattan resigned his job at the steelworks.
On 6 March 1952, Lily Volpert, a 42-year-old, was found murdered in her outfitter's shop in the Cardiff Docklands area. Her throat had been cut with a razor, and about £100 (equivalent to £2,595 in 2015) had been stolen. Within a few hours Mattan was questioned by the Cardiff City Police and ten days later he was charged with Volpert's murder. When the police raided Mattan's home they discovered a broken shaving razor and a pair of shoes with blood specks on them. There was no evidence of any blood-stained clothing or the missing money.
The trial took place at the Glamorgan Assizes in Swansea in July 1952. The main witness for the prosecution was Harold Cover, a Jamaican with a history of violence, who later received a share of a reward of £200 (equivalent to £5,190 in 2015) offered by the Volpert family. Cover claimed to have seen Mattan leaving Volpert's shop, though it later emerged that he had previously identified another Somali living in the area at the time, Taher Gass, as the man he had seen. The jury was not told of this, or of Cover's background during the trial. Neither was the jury informed that four witnesses had failed to select Mattan from an identification parade. One 12-year-old girl, who saw a black man near the shop at the time of the murder, and was confronted with Mattan, stated that he was not the person she witnessed, but the police ignored her statement and did not take the evidence to court. Furthermore, the shoes belonging to Mattan with specks of blood were second-hand, and no forensic information was brought forward linking the samples.
Mattan was described as having a limited understanding of English, and refused the services of an interpreter. In a trial slanted with racial overtones, Mattan's barrister described his client as "Half-child of nature; half, semi-civilised savage". These comments are likely to have prejudiced the jury and undermined Mattan's defence, particularly since they came from Mattan's own barrister, who had the task of defending him. On 24 July 1952, Mattan was convicted of the murder of Lily Volpert and the judge passed the mandatory sentence of death.
Mattan was refused leave to appeal and to call further evidence in August 1952, and on 3 September 1952, six months after the murder of Volpert, he was hanged at Cardiff Prison. He was the last person to be hanged at the prison.
In 1954 Taher Gass was convicted of murdering wages clerk Granville Jenkins. Gass was found insane and sent to Broadmoor; after his release he was deported to Somalia. In 1969 Harold Cover was convicted for the attempted murder of his daughter, using a razor. Mattan's middle son, Omar was found dead on a Scottish beach in 2003, and an open verdict was returned.
The Mattan family's first attempt to overturn the conviction was denied in 1969 by the Home Secretary James Callaghan; by this stage, three years had passed since the death penalty's abolition.
In 1996 the family was given permission to have Mattan's body exhumed and moved from a felon's grave at the prison to be buried in consecrated ground in a Cardiff cemetery.
When the Criminal Cases Review Commission was set up in the mid 1990s, Mattan's case was the first to be referred by it. On 24 February 1998 the Court of Appeal came to the judgement that the original case was, in the words of Lord Justice Rose, "demonstrably flawed". The family were awarded £725,000 compensation, to be shared equally among Mattan's wife and three children. The compensation was the first award to a family for a person wrongfully hanged.