The Birmingham Six were Hugh Callaghan, Patrick Hill, Gerard Hunter, Richard McIlkenny, William Power and John Walker. They were sentenced to life imprisonment in 1975 for two pub bombings in Birmingham on November 21, 1974 that killed 21 people. Their convictions were overturned by the Court of Appeal on March 14, 1991.

The Birmingham bombings were credited to the Provisional IRA, although the group denied this two days later. The devices were placed in two central Birmingham pubs: the Mulberry Bush, at the foot of the Rotunda, and the Tavern in the Town, a basement pub on New Street. The resulting explosions, at 20.25 and 20.27, collectively were the most injurious terrorist blasts in mainland Britain; 21 people were killed (ten at the Mulberry Bush and eleven at the Tavern in the Town) and 182 people were injured. A third device, outside of a bank on Hagley Road, failed to detonate.

The six men arrested were all Belfast-born but had lived in Birmingham since the 1960s. Five of the men, Hill, Hunter, McIlkenny, Power and Walker, had left the city on the early evening of the 21st from New Street Station, some hours prior to the explosions, to travel to Belfast to attend the funeral of James McDade, an IRA member who had accidentally killed himself while planting a bomb in Coventry. They were seen off from the station by Callaghan. When they reached Heysham they and others were subject to a Special Branch stop and search. The men did not tell the police of the true purpose of their visit to Belfast, a fact that was later held against them. While the search was in progress the police were informed of the Birmingham bombings. The men agreed to be taken to Morecambe police station for forensic tests.

On the morning of the 22nd, after the forensic tests and routine questioning, the men were transferred to the custody of West Midlands police. All men were interrogated by Birmingham CID and claimed that they were beaten, threatened and forced to sign statements written by the police over three days of questioning. Callaghan was taken into custody on the evening of the 22nd.

The men first appeared in court on the following Monday, the 25th, and were remanded in custody and taken to HMP Birmingham, Winson Green. At the prison the six men claimed they were subject to further ill-treatment. When they reappeared in court on the 28th all the men showed visible bruising and other signs of violence. In June 1975 fourteen prison officers were charged with varying degrees of assault but were found not guilty. In 1977 the six men pressed charges against the West Midlands police; these charges were dismissed under issue estoppel.

On May 12, 1975 the six men were charged with murder and conspiracy to cause explosions. Three other men, James Kelly, Michael Murray and Michael Sheehan, were charged with conspiracy and Kelly and Sheehan also faced charges of unlawful possession of explosives.

The trial began on June 9, 1975 in Lancaster. After legal arguments the statements the men had made in November were deemed admissible as evidence. The accused repudiated the confessions at the trial. The other evidence against the men was largely circumstantial, through their association with IRA members. Although Hill and Power had tested positive for the Griess test for handling explosives the later sample tests were inconclusive. The jury found the six men guilty of murder and on August 15, 1975 they were sentenced to life terms. In March 1976 their appeal was dismissed.

Their third appeal, in 1991, was successful. New evidence of police fabrication and suppression of evidence, the discrediting of both the confessions and the 1975 forensic evidence led to the Crown offering no case against the men. In 2001 the six men were awarded compensation ranging from £840,000 to £1.2 million.

The collapse of the case and other miscarriages of justice caused the Home Secretary to set up a Royal Commission on Criminal Justice in 1991. The commission reported in 1993 and led to the Criminal Appeal Act of 1995 and the establishment of the Criminal Cases Review Commission in 1997.