Police and drink drive limits revisited

I'd earlier noted that police in New Zealand are basically exempt from drink driving legislation: the courts note that they'd lose their jobs if convicted, view the punishment as exceeding the severity of the offense, and so discharge them without conviction.

So some police officers are able to take advantage of the stringency of their employer's attitude toward drink driving convictions to get leniency from the courts.

Radio New Zealand today reports on how a police legal advisor phoned Air New Zealand about a flight attendant's drink driving charge. The police did not inform the court that they were trying to get her fired, so she received the normal penalty and, in addition, was fired.

Classy stuff. I'll be cheering on the EPMU's complaints with the Police Complaints Authority and the Privacy Commissioner.

It could be worse. At least here they don't shoot unarmed civilians.

Police and drink drive limits

Well, this, from the front page of the Monday Christchurch Press, puts police support for ever-lower drink drive limits in a fresh light, doesn't it?

Half of all police officers caught drink-driving in the past three years have beaten the charge, raising allegations of one law for police and another for the public.

Three officers are still fighting their cases in the courts, including one caught driving while more than three times the legal limit.

Even the police's top personnel manager admits it is hard to secure a conviction against an officer.

The average conviction rate for all drink-drivers in the past three years was more than 95 per cent, compared with less than 38 per cent for police officers.

That's for the cases where charges are laid. One hypothesis could be that police hold their own to a higher standard than the public and so lay charges even in cases where they think the evidence insufficient; in that case, the numbers above overstate court bias in favour of police. An alternative hypothesis is that police are less likely to lay charges against other officers, in which case the numbers above understate bias in favour of police.

Drunk driving limits and risk aversion

John Key's National Government, elected partially due to public annoyance at Labour's "nanny state" initiatives, is talking about lowering the drink driving limit from 0.08 to 0.05.

David Farrar rightly asks, given that the vast bulk of drunk drivers killed in car crashes had well over 0.08, would the reduction in deaths among folks in the 0.05-0.08 range be worth the cost in terms of reduced enjoyment of nights out.

I've heard rebuttals of this question pointing out that most drivers who have wine with dinner are in fact under the 0.05 limit anyway and so would not be affected. This seems a nonsense though. It's difficult to know with certainty what your blood alcohol level is after any given quantity of beer or wine, so sensible folks who weigh heavily the costs of being caught over the limit will target a level sufficiently below 0.08 that they will not err and be over the limit. The wider the confidence interval around your point estimate, the lower will be your targeted level to avoid the risk of erring on the upside.

So, if the limit is dropped from 0.08 to 0.05 and most folks currently target somewhere around 0.04, their drinking, and their enjoyment of a night out, will drop considerably even though the dropped limit remains theoretically unbinding. And the folks who are happy to be caught for the 10th time driving on a suspended license at four times the legal limit will continue to ignore the limit.

Isn't it better to have a sensible limit with heavy punishment rather than a low limit that cannot have a punishment sufficient to deter the really dangerous folks? With a limit at 0.08, really dangerous anti-social deviants like this guy can have the book thrown at them; with a limit at 0.05, there would be no support for heavy punishment because the net is cast too wide.