Under influence of legal advice?

Northland police are on the roads 24 hours a day in an effort to reduce drink- driving.Photo / John Stone

The number of blood samples analysed by police in Northland has declined 18 per cent since 2013 - and a Northland barrister says it may be because more drink-drive defendants are taking advice from lawyers.

In the Northland policing district, 188 blood samples were analysed in 2011.

That number fell to 154 in 2013. Similar declines have occurred across the country, police statistics show.

A few years ago "a lot of technicalities existed to allow drink-drivers to be found not guilty", Whangarei defence lawyer Dave Sayes said.

"I have had clients who've blown up to 430mcg before, and they've asked for a blood test, and the blood test has come back under the limit because of the length of time it takes the nurse to arrive.

"I can take up to seven drink-driving calls a night. I say to people, 'If you're blowing over 430mcg, don't bother with a blood test'. The Bill Of Rights Act came in in 1990. Up until then, defendants didn't have a right to a lawyer."

As a result a decrease in people electing to have a blood-alcohol test might be attributable to responsible advice from lawyers, Mr Sayes said.

National manager of road policing Carey Griffiths said "anybody charged will be asked to pay the cost of medical analysis", adding the reduction in blood and breath samples was attributable to wider influences including alcohol licensing restrictions, NZ Transport Agency campaigns and ongoing police testing.

Lowering the breath-alcohol limit to 250mcg from December 1 had been another influence. "We regularly strike people who think the drink-drive limit's been lowered already."

Drivers who refuse an evidential breath test must undergo a blood test.

Ten minutes quiet time or time to speak with a lawyer is afforded to anyone after a breath screening test but before an evidential or blood test. Courts will take the results of a blood test over the results of an evidential breath test.

Independent medical staff usually take the blood samples as legislation prevents police from taking blood tests.

Drivers also have the option of asking for their blood test to be conducted by an independent analyst.

Transport statistics show 8000 drivers are annually convicted of drink-driving offences, with 1600 drivers a year refusing to provide a blood sample.

Land Transport Amendment Bill changes will lower the breath-alcohol limit for adult drivers to 250mcg per litre of breath from December 1. The blood limit will reduce from 80mg of alcohol per 100ml of blood to 50mg.

Section 67 of the Land Transport Act 1998 says any person convicted of an offence under the act "is liable to pay the blood test fee" and "any associated medical expenses".