The NSW "one-punch" laws are likely to blow out costs in the legal system and are essentially unnecessary, according to a University of Wollongong academic.
Premier Barry O'Farrell unveiled a series of measures on Tuesday aimed at reducing one-punch attacks, including creating a new offence for fatal assaults involving alcohol and drugs that will carry a mandatory minimum jail sentence of eight years and a maximum of 25 years.
Mandatory minimum sentences will also be introduced for nine existing violent offences in cases where alcohol and drugs are involved.
Other measures include 1.30am lockouts and 3am closures of venues in the Sydney CBD and Kings Cross while bottle shops across the state will have to close their doors at 10pm.
The measures are a response to the public outcry for action in the wake of the deaths of Thomas Kelly in 2012 and Daniel Christie this month.
Julia Quilter, a senior lecturer in UOW's Faculty of Law, Humanities and the Arts, praised the tighter measures on venues and said they continued the work the government had been doing in the wake of Mr Kelly's death.
In 2012, the government introduced what Dr Quilter called a "multi-faceted and nuanced response" that included tightening hotel licensing, improving CBD public transport and alcohol education campaigns.
However Dr Quilter, who has been researching Australia's one-punch laws since the sentencing of Mr Kelly's killer Kieran Loveridge, said the introduction of a new offence and mandatory minimum sentences were "a knee-jerk law and order response".
A former solicitor and barrister, Dr Quilter said so-called one-punch laws were in effect in Western Australia and the Northern Territory.
They were introduced to fill a gap in the manslaughter law that didn't exist in NSW, she said.
In NSW the existing manslaughter laws effectively cover incidents such as one-punch assaults.
"Our manslaughter laws have always covered this situation and when I looked at all the one-punch cases in NSW, of which there was 18, we are getting convictions," Dr Quilter said.
Her study of prosecutions under these laws reveal that what follows is either the laws are never used (as is the case in the Northern Territory) or there are a range of unintended consequences (as in Western Australia).
"When I started researching those prosecutions it became very clear that the Western Australian offence was modelled on a one-punch scenario [but] that was the minority of matters being prosecuted under that offence," she said.
"What we saw was very serious domestic violence matters where there was an ongoing history of abuse and violence and, at some point, an assault was made on the woman and the woman was killed.
"That was never what was perceived to be why these laws were being produced but that was the unintended consequence in the Western Australian context."
The proposed NSW law differs in one crucial way - it includes a mandatory minimum of eight years.
Dr Quilter felt this difference would lead to a range of flow-on effects that would place an added burden on the legal system.
"First of all we're not going to see early pleas to these types of offences," she said.
"Why would you plead to something you know you're going to get a mandatory minimum of eight years?
"Our whole guilty plea system is based on producing efficiency for the community both in terms of not running lengthy and costly trials but also of not having to put the victims through the horror of going through a trial.
"All that goes when you have mandatory minimums in place because the defence will want to put the Crown to the test on every single element.
"You'll get much longer trials which will be extremely well contested, which ups the cost of criminal justice in NSW."
Other effects would be cost increases for legal aid and, ultimately, the extra cost of housing offenders in jail for longer periods.
It would also create an imbalance in the system where more serious offences didn't attract a mandatory minimum sentence.
While mandatory minimums might offer some sense of justice for the families of the victims, Dr Quilter said there was no evidence increasing sentences changed the behaviour of offenders.
"Let's put it this way, if you're drunk and it's 3am and you're angry, is the first thing you think about if you have a confrontation with somebody, 'gee if I hit this person and they die I could be liable for eight years jail'?" she said.