Can an accused person obtain evidence that could conceivably help him defend himself against a drinking driving charge?

I agree with the reasoning of Wooton, J., in Regina v. Johnstone (supra) that an accused person should not be prevented from obtaining evidence which could conceivably help him to defend himself in respect to a drinking driving charge. There are, in my view, limiting factors to this proposition. Firstly, a request for the obtaining of the evidence should be a bona fide request on the part of the accused. Secondly, the circumstances existing at the time of the request should be such that it would be reasonable for the request to be granted.