Research from University of Limerick, Ireland reveals that long prison sentences are as effective as the death penalty in deterring homicides

Press release (10/4/25)

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Lengthy prison sentences can be as effective as the death penalty in deterring homicides, according to new University of Limerick, Ireland research.

The study, published in the Southern Economic Journal and co-authored by Dr Vincent O’Sullivan, Associate Professor at UL’s Kemmy Business School, examined the effect of capital punishment and life sentences on homicide rates.

According to the research – which closely examined the Australian legal system and its history with capital punishment – the death penalty had a deterrent effect on homicides, resulting in an estimated 7.6 percent reduction in the crime.

Additionally, Dr O’Sullivan and his co-author, Dr Hugh Farrell, examined more recent policies existing in parts of Australia, including Standard Non-Parole Periods (SNPPs), under which those convicted of murder will receive a life sentence but, typically, must serve a minimum 20 years.

They found that these SNPPs, which take discretion away from judges and parole boards in setting minimum prison sentences, had the same deterrent effect on homicides that the death penalty had.

Dr O’Sullivan commented on the significance of the study findings, particularly for countries like the United States, where the death penalty still exists.

“Our research is informative for policy makers considering abolition of the death penalty,” explained Dr O’Sullivan.

“The US is at a crossroads when it comes to the death penalty. Its usage had been declining since the 1990s and several large states such as California and Pennsylvania are on the cusp of abolition. However, the Trump administration has indicated that it is very much in favour of the death penalty, so there will be much debate on this over the next few years.”

The researchers examined the history of Australia, from just after its founding, to the present day. Australia last used the death penalty in 1967, and most states had abolished it by the end of the 1970s.

“Australia is worth studying because different states and territories had different systems at different times. It's also worth studying capital punishment in Australia because it was used much more frequently than the USA. Another advantage of examining Australia is there were not extremely long waits on death row as happens in the USA,” explained Dr O’Sullivan.

For countries like Australia, where capital punishment is no longer legal, Dr O’Sullivan said that the research confirms the deterrent effect of standard non-parole periods.

“Some people might not want to remove discretion from judges and parole boards when it comes to sentencing. On the other hand, there is a public safety argument for lengthy and definite prison terms for the worst crimes in our society,” he said.

The publication of the research is timely considering recent political discourse around capital punishment and issues of morality surrounding the death penalty, particularly in the US, where it is currently legal in 27 states and at the federal level.

“That is not to say that the death penalty should be re-introduced [where it is not currently legal]. There are many moral problems with such punishment, not least the problem of wrongful convictions,” said Dr O’Sullivan.

“There is also controversy around the method of execution. In the US, pharmaceutical companies don't want to supply drugs for lethal injection, so states are having to change their lethal injection protocols, or else use poisonous gas or even firing squads.”

ENDS

The study, ‘Homicide, punishment and deterrence in Australia’, by Hugh Farrell and Vincent O’Sullivan, has been published in the Southern Economic Journal.

Please note that further comment can be provided by Dr Vincent O’Sullivan, upon request.

For further information, please contact:

Jane Haynes

Faculty Marketing & Communications Officer

University of Limerick 

+353 87 755 5946 

jane.haynes@ul.ie

About University of Limerick:

University of Limerick is a research-led, independent, internationally focused university with almost 18,000 students and 2,000 staff. It is a young, energetic and enterprising University with a proud record of innovation in education and excellence in research and scholarship.

More information is available at https://www.ul.ie./

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