He spent much of his time examining crime scenes, and later scenes of crime exhibits for the purposes of presenting expert identification testimony in Irish courts. He retired from An Garda Síochána in 2023. 

His story is doubtless of interest to citizens of Ireland and elsewhere, not least Scotland, but those unfamiliar with the geography of the Republic might have found it helpful to have a map. 

The Sweetman family accompanied John on his first journey by car before a motorway was built, to the Garda College, in County Tipperary, for a training course that started in 1993.

The journey, the reader is told, was from Dublin “through Kildare, Monasterevin, Ballybrittas, Portlaoise, Mountrath, Borris-in Ossory, Roscrea and then on finally to Templemore”: it all sounds very nice.  

There are, as it were, two lines of inquiry: first, there is a story of someone taking his work seriously, explaining how he obtained his qualifications and achieved the standard of a skilled specialist in two difficult areas.

There are many descriptions of attending distressing scenes of major crimes, and criminal trials and similar appearances as a witness in the Coroner’s Court.

Rather disparaging comments by the detective garda are made about some of the lawyers he has to deal with, but that is not unknown amongst lawyers about other lawyers.

He may have some grounds for his dismay, examples abound: when, as a document examiner giving evidence in court about a counterfeit cheque in an envelope, he was asked numerous questions in cross-examination as to whether the envelope was also counterfeit.

Secondly, there are the professional pressures, and the inherent personal difficulties of becoming and then being a police officer in the Republic.

All that is likely to be familiar international territory, and the descriptions and explanations of personal illness are unquestionably sad.

The effects of the ‘modernisation’ of the Garda, particularly with new IT, is likely to have been greatly understated in the telling, but it will be read as uncannily familiar to others elsewhere.

The real value of the book lies in the lucid and helpful explanations in plain language of the technical and scientific basis of the scientific work of a specialist.

Identity: Murder, Fraud and the Making of a Garda Forensic Expert by John Sweetman. Published by Hachette Books Ireland, 323pp, £15.99.