The Grangegorman killings refers to the homicide on 6 March 1997 of Sylvia Shields and Mary Callinan, patients of St Brendan’s Psychiatric Hospital in Grangegorman, Dublin, Ireland. After giving a false confession, Dean Lyons was charged with the murders and placed on remand. In his statement to the Irish police force, the Garda Síochána (commonly called the Gardaí), Lyons gave details that would only be known to the murderer or to the investigators. After Lyons was charged, Mark Nash confessed to the killings, but later retracted his confession. In April 2015, Nash's trial for the murder of Shields and Callinan began after an unsuccessful attempt to prevent the trial from going forward.

Lyons was described by one of the gardaí (policemen) involved in the case as a "Walter Mitty" character, and Dr Charles Smith, psychiatrist and director of the Central Mental Hospital, Dundrum, felt that he might be prone to exaggeration and attention seeking. A commission of investigation was set up to investigate the conduct of the gardaí in the case. Dean Lyons died from a heroin overdose in 2000. He spent nine months in jail for a crime that he did not commit.

Grangegorman (Irish: Gráinseach Ghormáin) is a suburb on the northside of Dublin city, Ireland. The area is administered Dublin City Council. It is also a civil parish in the historical barony of Dublin. It is best known as the location of St Brendan's Hospital which was the main psychiatric hospital serving the greater Dublin region. Along with Stoneybatter and Glassmanogue, Grangegorman was recorded in 1610 as one of only three remote villages in this region and at that stage, lying north of Ostman town and north of the River Liffey. They were not joined to the city of Dublin. The area is currently the subject of a major redevelopment plan under the aegis of the Grangegorman Development Agency.

Etymology

The name Grangegorman, as with other placenames containing the name "gorman" in the Leinster region, probably indicates that at one time this territory was held by the Uí Bairrche, an Irish clan based in Leinster. The two main representatives of this clan were Uí Treasaig (Tracey) and Mac Gormáin (MacGorman). They were displaced following the Norman invasion of Ireland from the twelfth-century.