It’s always struck me as a bit odd, the disparity between the NZ drug driving law and the drink driving law.
My non-lawyer’s view is that drug driving law stipulates that a person is guilty of the office if their blood contains evidence of a qualifying drug. This means that if even a small amount of any of the usual drugs of abuse or other drugs such as some prescription medications is found in a person’s blood, and they have also ‘failed’ a compulsory impairment test then the person can be found guilty of the offence.
It’s not as simple as that of course because there are other legal and procedural issues, but the point to make here is that merely the presence of any qualifying drug goes a long way to the likelihood of a successful prosecution. Even if the concentration of that drug is not sufficient to cause impairment in itself; the analysis at the laboratory does not allow any comment on whether or not the concentration present is capable of causing impairment. The analysis just has to show whether or not there is any qualifying drug present; there is no requirement to report any concentration of the detected drug/s.
The drug driving law uses a combination of the results of the compulsory impairment tests, the results of which are subjective and based on the experiece of the police officer who conducted them (and who is not usually medically trained) with the results of a blood test that do not have to show a concentration of a drug but just demonstrate the presence of a qualifying drug.
Compare this with the drink driving law, which states that people can legally drive around in their cars with blood alcohol concentrations more than capable of causing impairment but as long as their blood alcohol concentration is below 80 milligrams of alcohol per 100 millitres of blood then they’re not committing an offence.
Seems inconsistent to me to have one drug (alcohol) permitted in blood at a concentration more than capable of causing impairment below a level of 80 mg alc/100 ml blood whilst all other drugs only need to be demonstrated to be present, along with a ‘failed’ impairment test.
A lower legal blood alcohol concentration would seem, to me, to bring the drink driving law more in line with the drug driving law.