Violent assaults mostly by drunks

Most weekend assaults are by drunk young men, many of whom have had more than 22 standard drinks and blame the intoxication for their violence, a study shows.

The research was released by the Australian Institute of Criminology before this weekend's Operation Unite, a national police crackdown on drunken violence.

It analysed interviews with offenders at nine sites around Australia, including the East Perth lockup, between June 2009 and December.

People arrested for assault or disorderly conduct between 6pm and 6am on Fridays and Saturdays were more likely to have had big quantities of alcohol than those detained during the week.

Those charged with assault reported having had a median of 14 standard drinks, equal to nine schooners of beer, while those picked up for disorderly conduct had 15.

For weekend assaults, 70 per cent of perpetrators had been drinking, compared with 50 per cent at other times. Of those, 66 per cent said the alcohol was a factor.

Young men aged 18 to 25 made up 45 per cent of assault arrests at weekends and were most likely to have mixed beer, wine and spirits.

This group of offenders reported the highest alcohol intake: 22 standard drinks, the equivalent of a 700ml bottle of spirits. Only 12 per cent of those arrested were female.

These young men were also the people most likely to be arrested for disorderly conduct.

But older male offenders, aged 26 to 35, were the biggest drinkers. Those who mixed their drinks had a median of 29 standard units in a night, which equates to just over three-quarters of a case of full-strength beer.

Professor Steve Allsop, director of the National Drug Research Institute at Curtin University, said drinking such an enormous amount made people a danger to themselves and others.

"They are more likely to be swinging wildly without thinking about what they're doing," he said.

"Violence results from a combination of factors but we only have to look at the sheer level of intoxication and crowding to see it makes an already risky situation worse."

Assaults were the reason for 17 per cent of police arrests but that figure jumped to 21 per cent at weekends, the report found.

The data did not include offenders who were too drunk or violent to be interviewed.

The researchers also found just over half those arrested for assault at weekends had their last drink at a private home, 30 per cent were at licensed premises.

The latest AIC data on drug use, from 2008, showed 35 per cent of offenders taken to East Perth lockup tested positive for methamphetamine, the highest level of the monitored sites but lower than its level in 2001.

The national average was 21 per cent.

The Australian Hotels Association (WA) has called for all offenders to be tested to give an accurate picture of the contribution of drugs to violence.

Police statistics also show per-capita assault rates have changed little over the past 10 years but those that caused grievous bodily harm had increased one-third.