Area of Law – Driving – Drink Driving Offences
An Article about Use of expert evidence and defending drink driving offences
What are the limitations (if any) of calling expert evidence in defence of a charge under s. 49(1)(f)
It is a defence to a charge under s. 49(1)(f) to establish that the breath testing instrument was not working properly at the relevant time the sample was taken and recorded (see section 49(4) of the Road Safety Act 1986). However s. 49(6) provides “In any proceedings for an offence under paragraph (f) or (g) of subsection (1) evidence as to the effect of the consumption of alcohol on the defendant is admissible for the purpose of rebutting the presumption created by section 48(1A) but is otherwise inadmissible”.
A case which dealt with the two conflicting provisions was DPP v Hore; DPP v Askwith  VSCA 192. In that case the defendants had called expert evidence from a consulting chemical analyst who performed tests on the alcohol elimination rates of both men, by taking their blood samples after consumption of alcohol.
Over objection from the prosecution, the expert was allowed to give evidence as to the results of his experiments on both men. His evidence was to the effect, that the readings were unusually high, and could be attributed to the men consuming more alcohol on the particular occasion or the result of a faulty machine. The Magistrate dismissed the defendants on both charges. On appeal to the Supreme Court the decision was upheld.
The DPP appealed to the Court of Criminal Appeal. The Court ruled that the evidence given by the expert was inadmissible and should have been excluded through the application of of s. 49(6) as that evidence was evidence “as to the effect of the consumption of alcohol on the defendant”.