Drug Driving Cases – Advice for Solicitors

Background

IDMU has been providing expert evidence since 1999 on drug-driving cases involving cannabis, amphetamines, cocaine, ecstasy, opiates and benzodiazepines.  We are aware that many solicitors do not encounter such cases on a regular basis, and would offer the following advice to all solicitors dealing with such matters in the UK.

The law prohibits driving and other driving-related activities if the person in charge of the vehicle is ‘unfit through drink or drugs’, the definition of unfit is that his or her ability to drive ‘properly’ is impaired.  It is not a traffic offence simply to be under the influence of drugs, nor is there currently any drug-driving ‘legal limit’ such as with alcohol.

Driving Behaviour – Was the defendant arrested following an accident, moving traffic offence or erratic driving behaviour?  Could unfitness at the time be implied by the driving behaviour?  In such cases the evidence of lay or police witnesses as to the driver’s behaviour may be adduced.

In other cases drug-driving charges are brought ‘opportunistically’ as a result of drugs being found in the vehicle, the vehicle smelling e.g. of cannabis, or admissions as to drug use by the defendant during questioning.

Elements of the offence(s)

The quality of prosecution evidence can vary considerably, but in order to succeed a prosecution must show the following three elements in proving the offence:

(a) The driver must be demonstrated to be under the influence of a drug or drugs at the relevant time (via forensic testing of bodily fluids)

(b) The driver must be shown to be impaired and unfit to drive

(c) The impairment must be due to drugs rather than some other cause (e.g. fatigue, shock, physical or mental disability)

Evidence of Intoxication/Being Under the Influence

Forensic evidence as to presence of quantifiable active drug or active metabolite in a blood sample

(a) Presence of inactive metabolites (e.g. THC-COOH also referred to as carboxy-THC or THC-acid for cannabis, Benzoylecgonine for cocaine) does not prove intoxication at the relevant time

(b) Presence of active drug or active metabolites (free THC or active metabolite 11-hydroxy-THC for cannabis, free cocaine etc) in the sample at quantifiable levels will normally demonstrate that the defendant was under the influence at the relevant time

(c) Note that the marker for heroin use is 6-monoacetylmorphine (6-MAM), findings of morphine alone could arise from e.g. codeine-based painkillers.  If the prosecution are alleging heroin use it is incumbent on them to test for 6-MAM in the sample.

(d) The half-life in blood of active drugs/metabolites can be short in some cases, therefore a long delay between the incident and a sample being taken can eliminate these substances from the system or greatly reduce their concentrations.

Urine:  Urine samples are not normally used because they do not generally allow the time of any intoxication to be determined.  However where the defendant refuses a blood test but offers a urine sample the court might in those circumstances regard a positive sample as implying use of the drug around the relevant time.

Saliva? IDMU has recommended use of saliva samples which offer many of the forensic advantages of blood with the convenience (non-invasiveness) of urine, however there is no legal provision for these at present.  Taking saliva samples at the time of initial arrest and again contemporaneously with the evidential blood sample could indicate whether a given level represents recent use (falling saliva levels) or residual baseline levels (stable saliva levels) from use in the more distant past.

Evidence of Impairment

Fitness to drive is normally assessed by way of an impairment test, normally conducted at the police station by trained officers and/or a forensic medical examiner.

Impairment Tests:  The five tests are a papillary examination (pupil size and state of eyes), Romberg test (comprehension, time estimation/balance), walk & turn test (comprehension, balance), one-legged stand (balance) and finger to nose test (comprehension, coordination, balance).  The performance of ‘normal’ individuals can vary widely, as the balance tests disadvantage older or overweight subjects, hand-eye coordination skills (e.g. finger to nose) is likely to be better in persons involved in skill-sports, and if one never has had the need to estimate time in a number of seconds, the Romberg test performance can be wildly inaccurate.

Many of the tests are highly subjective and can be influenced by prior knowledge on the part of the tester (e.g. that the subject had admitted using drugs, that drugs were seized, or drug use was strongly suspected).  IDMU has recommended quality-control testing of testers, and that the tester is not made aware of why a subject is to be tested.

Video/CCTV - It is strongly recommended that all such tests be recorded on video or CCTV, preferably with audio, and that all footage of a defendant in custody is demanded and shown to the court, to allow the court to form an objective view as to the condition of the subject.

In cases where CCTV footage has been obtained the findings of unfitness have been overruled by the court where the footage has shown the defendant to be acting/speaking normally on admission to custody, or standing steadily for extended periods without swaying, or where demonstrations of the test by officers have been incorrect (e.g. officer taking the wrong number of steps in the walk-and-turn test then failing the defendant for the same reason).

Evidence of Impairment Due to a drug

A finding of unfitness is required before a bodily fluid sample (normally blood) can be required.  A doctor (FME) must be satisfied that impairment may be due to a drug.

Note that it usually takes around 15-20 minutes to complete all the impairment tests so if the medical examination is shorter than this the FME may not have had reasonable opportunity to form a view as to whether or not the subject is impaired.

Police officers may be trained to conduct tests and record the results but they do not have the medical training to determine whether a subject is impaired or the reason for any such impairment.

Many FMEs are from overseas and their command of English can vary widely.  Where the first language of the FME (or subject) is not English, confusion can arise as to the instructions given causing a subject to fail the test.  Again the command of English of the FME should be tested in court

Effects of Drugs on Driving

Not all drugs impair driving ability, and different individuals vary as to the level of impairment a given dose of a drug might produce.  The effects on ability do not tend to be as linear as those found with alcohol, although in general higher doses tend to be more impairing than lower doses.

The main effects of different types of drugs can briefly be summarised as follows:

Cannabis – The effects of cannabis very much depend on the experience of user both of cannabis use and of driving.  Cannabis tends to impair tracking ability and judgement in some cases, however drivers under the influence tend to drive more conservatively resulting in little epidemiological evidence of increased accident risk.  There is little effect on reaction time, may even reduce reaction time in some cases.  The highest increase of risk is for young drivers, particularly females, with little effect in experienced users.  Note that the effects of cannabis rarely persist beyond 2 hours and any finding of impairment more than 2 hours after an incident is likely to arise from other causes (or be erroneous).

Amphetamine/Cocaine – stimulants in low doses can increase alertness and improve performance (e.g.. amphetamine pills given to RAF pilots during combat missions), high doses can impair judgement (e.g. making the user ‘jumpy’ and likely to over-react) and lead to more aggressive driving behaviour, with psychotic reactions in extreme cases of heavy or prolonged use.  Comedown effects can lead to excessive fatigue and drowsiness.

Opiates – Little effect in experienced users although withdrawal can impair performance.  Sedative effects in naïve or occasional users impairing performance.  Effect of a moderate dose for an addict would be to make him/her feel ‘normal’.

Benzodiazepines – Depressant drugs leading to drowsiness and inattention, can be disinhibiting like alcohol, clear evidence of impairment and substantially increased accident risk.

Ecstasy – Evidence of increased accident risk compared to other stimulants.

Summary

For a prosecution to succeed, they need to provide the following evidence

1 – Witness evidence as to reasons for the stop (e.g. police/lay witnesses to erratic driving, accident etc and condition of driver when stopped, why drugs are suspected)

2 – Full details of defendant’s performance on impairment tests (copies of pro-forma e.g. form MG-DDG)

3 – Statement from FME as to findings of impairment including reasons for suspecting this may be due to a drug

4 – Forensic evidence of presence of active drugs or active metabolites in the blood sample

Solicitors are strongly recommended to demand copies of any CCTV footage of the defendant in custody and/or during performance of impairment tests.

© IDMU Ltd October 2011