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.