Forensic aspects of alcohol, drugs and driving
Driving under the influence (DUI) of alcohol (DUIA) or drugs (DUID) is responsible for thousands of accidents each year (National Highway Traffic Safety Administration 1993; Wennig and Verstraete 2000). In many countries, laws have been introduced to control drink-driving together with procedures to detect and prosecute impairment, and to treat and rehabilitate offenders. Alcohol is clearly still the largest contributor to impaired driving, but the additional impact of drug impairment on driving has also become a focus in recent years. Forensic toxicologists play an important role in many aspects of DUI, particularly in measuring the pharmacological relationship between drug or alcohol use and impairment. They have a primary role in analysing samples from drivers suspected of being impaired, interpreting results and presenting information in court. The consequences to the offender (arrest, detention, trial, legal expenses, fines, loss of licence, imprison ment) are serious, and defendants deserve assurances that laboratories carrying out measurements employ appropriate analytical safeguards and standards, and that individuals who interpret results have the necessary education and qualifications. A typical scenario for procedures relating to DUI is as follows:
1. Police see a vehicle being driven erratically or are called to the scene of an accident.
2. Police question the driver and look for signs of impairment .
3. Police assess impairment using tests such as the horizontal gaze nystagmus test and walk and turn test (see Fig. 11.2).
4. Police carry out roadside screening tests for breath alcohol (BrAc) and/or drugs.
5. If tests indicate the driver is over the legislative limit for BrAc and/or if drugs are present, the driver is taken to a police station or other authorised test facility and an evidential breath alcohol test carried out and/or a sample of blood taken for laboratory testing.
6. The blood sample is analysed for blood alcohol by headspace gas chromatography (Fig. 11.3) (if evidential BrAc testing has not been carried out) and for the presence of drugs if impairment through drugs is suspected. 7. The driver may be prosecuted depending on the test results and circumstances of the case.
