Criminologist who argued for a humane justice system

Paul O’Mahony, who has died aged 69, was an eminent psychologist, criminologist and campaigner for the more progressive and constructive treatment of prisoners. He published six books and a wide range of articles, with a particular focus on the criminal justice system in Ireland.

His colleague Kevin Warner said his work was academically rigorous, but its core quality was “always a seeking out of truth, often the uncomfortable truth, and, most especially, he spoke truth to power”.

What came across strongly was the humanity in his research. “He could do the statistics, but we always see ‘the whole person’, people in all their complexity, their qualities as well as their problems, the lives they live, their backgrounds and experience. Through it all there is a deep commitment to social justice.”

The Irish Penal Reform Trust, which he co-founded, described him as "one of Ireland's pre-eminent advocates of penal reform", his stance being based on "exceptional research … as well as a profound moral sense".

Emigration

Paul O’Mahony was born in London, where his parents, Patrick, a buyer for a building company, and Katherine Nealon, a shop assistant, had emigrated from their native Limerick city during the second World War to find work.

Times were tough and accommodation hard to secure, so he was sent home to his grandmother in Limerick for a couple of years before returning to a council estate in Watford, where his parents were eventually housed.

He excelled at primary school and won a scholarship to St Benedict's public school in Ealing. He was thought to be an Oxbridge candidate and studied only Greek, Latin and ancient history in his final years in school. But he became disaffected, did poorly in his Oxbridge interviews and took a place instead at Trinity College Dublin.

He studied philosophy at Trinity and met his future wife, Sheila Greene, there. He first worked in the new world of computer programming but felt unsuited to it and returned to Trinity to get a second moderatorship in psychology.

Doctorate

After two years in the US, he and his wife returned to Dublin in 1973, where she took up a lectureship at Trinity. Job prospects being bleak, he returned to study, working for a doctorate in public attitudes to mental illness. This was followed by an MSc in statistics.

From 1981 to 1993, he worked as a psychologist in the Department of Justice, working at first with individual prisoners before looking at wider social and psychological issues. His early research on prison conditions received little attention and he increasingly challenged the Department of Justice to publicise his work, an attitude that did not make him popular with senior civil servants.

He published his first book, Crime and Punishment in Ireland (1993) without departmental support but by 1997, by which time he had left for a new job at Trinity, there was a new openness to research in the department, which published his next book, Mountjoy Prisoners: A Sociological and Criminological Profile.

He lectured in psychology and research methods in the department of occupational therapy in Trinity and was department head for three years. He continued to write academic books and articles and journalistic pieces on prisons, crime, drugs and criminal justice and often appeared on TV and radio, usually arguing for a more humane justice system. In 1994, he co-founded the Irish Penal Reform Trust and was a member of the National Crime Forum in 1998.

He had an abiding concern for justice and equality and his final book, The Irish War on Drugs: the Seductive Folly of Prohibition (1998), argued for the decriminalisation of drug use. Towards the end of his life, he felt discouraged about how little impact his work seemed to have had, stopped writing and concentrated on his many other interests in travel, photography, architecture and music.

He was an associate professor when he retired from Trinity in 2011. He had been diagnosed with cancer the year before but recovered, only to be diagnosed with a different cancer five years later. He is survived by Sheila, children Kit and Helen, grandchildren Arthur and Theo and brother Marcus.