When can the police perform a roadside drink or drug test?
Regular viewers of reality shows such as Traffic Cops or Police Interceptors will be all too familiar with drivers being tested at the roadside for alcohol or drugs. In this article we look at what the law surrounding roadside drink and drug testing actually says, and what this means for you if you are required to submit to testing.
The term “roadside test” is actually a misnomer. The technical term is actually “preliminary test” because there is nothing which says that the test must be carried out at the roadside. The power enabling the police to undertake a preliminary test comes from s6 Road Traffic Act 1988 (“RTA 1988”), and sections 6A-6C state that a preliminary test may be carried out:
(a) at or near the place where the requirement to comply with the test is imposed, or
(b) if the constable who imposes the requirement thinks it expedient, at a police station specified by him.”
It should, however, be noted that a preliminary breath test may only be carried out in accordance with (a) above, unless a constable reasonably believes that an accident has occurred owing to the presence of a motor vehicle on a road or other public place, and the person was driving, attempting to drive, or in charge of the vehicle at the time of the accident. In the latter case, the test may be carried out in accordance with either (a) or (b).
The purpose of a preliminary test is to enable the police to quickly and efficiently establish whether it is worth arresting a driver to investigate whether they were driving whilst under the influence of drink or drugs. If the preliminary test comes back positive, this is usually followed up by a more accurate “evidential” test at a police station pursuant to s7 RTA 1988.
When does a constable have the power to undertake a preliminary test?
According to s6(2)-(5) RTA 1988, a constable can require a driver to co-operate with one or more preliminary tests if a constable reasonably suspects that one of the following applies:
(a) The person is or has been driving, attempting to drive, or in charge of a motor vehicle on a road or other public place; AND EITHER
(i) has alcohol or a drug in his body or is under the influence of a drug; OR
(ii) has committed a traffic offence whilst the vehicle was in motion; OR
(b) The person:
(i) has been driving, attempting to drive or in charge of a motor vehicle on a road or other public place; AND
(ii) was doing this whilst having alcohol or a drug in his body or while unfit to drive because of a drug; AND
(iii) still has alcohol or a drug in his body or is still under the influence of a drug; OR
(c) An accident occurs owing to the presence of a motor vehicle on a road or other public place, and the person was driving, attempting to drive, or in charge of the vehicle at the time of the accident.
Note that the constable must only reasonably suspect the above to be the case in order for their power to undertake a preliminary test to be activated.
It should, however, be noted that under s9 RTA 1988 hospital patients are granted a degree of protection against preliminary testing. In cases where a constable wishes to perform a preliminary test on a hospital patient, the test cannot be performed if the patient’s doctor objects on the grounds that performing the test would be prejudicial to the patient’s proper care and treatment.
Three types of test
Under s6A-s6C RTA 1988, three types of preliminary test can be undertaken:
- Preliminary breath test. This is where the driver provides a specimen of breath which is then used to obtain an indicative reading from a breathalyser as to whether the proportion of alcohol in the driver’s breath or blood is over the prescribed limit. It should be noted that the breathalyser must be approved by the Secretary of State, and that its operating instructions should be followed.
- Preliminary impairment test. This is where the constable instructs the driver to perform certain tasks, whilst being observed by the constable, and the constable notes his observations of the person’s physical state. This test can only be performed if the constable in question has been properly trained, and if the test itself follows the Secretary of State’s Code of Practice issued for this purpose.
- Preliminary drug test. This is where a specimen of sweat or saliva is obtained and is used to obtain an indication of whether the driver has a controlled drug in his body, and whether the proportion of it in the person’s blood or urine is likely to exceed the prescribed limit. The device used to indicate the presence of drugs must be approved by the Secretary of State, and the test can be repeated up to three times.
Clearly, the type of preliminary test adopted will depend on the circumstances of the individual case. It is also well within the constable’s powers to insist that the driver complies with all three types of preliminary test, if he considers this to be appropriate.
Interestingly, a constable may only administer these tests if he is in uniform at the relevant time.
What if the police do not follow these rules properly?
Frustratingly, the impact of a failure to follow these rules is small. If the preliminary test is positive, the driver will almost always be arrested and taken to a police station for an “evidential” test under s7 RTA 1988. The evidential test is generally undertaken using more accurate equipment, and so produces a much more reliable reading than a handheld device intended for use at the roadside. Accordingly, the evidential test will provide the readings that will be used in court should the result come back positive, and the preliminary test is usually abandoned. Any question of the preliminary test being rendered inadmissible under s78 PACE (for example) is therefore largely redundant in practice. Furthermore, the courts have consistently held that an unlawful preliminary test does not prejudice the legality of the s7 evidential test save for in exceptional circumstances such as where the police use some form of trick or deception in obtaining the evidence.
What if you fail to co-operate with a test?
If a constable requires you to undertake a preliminary test, you must comply. A failure to comply without reasonable excuse is an offence under s6(6) RTA 1988 and can give rise to a fine, discretionary disqualification, or four penalty points. It should be noted that a claim from the defendant that the pre-conditions for requiring him to comply with the test were not present was considered not to amount to a reasonable excuse in relation to this offence. In reality, only genuine medical reasons are likely to amount to reasonable excuses.
Furthermore, under s6D RTA 1988, if you refuse to comply with a preliminary test and a constable suspects you have alcohol or a drug in your body, or that you are under the influence of alcohol or a drug, you can be arrested and taken for an evidential test under s7 RTA 1988 anyway.
The fact that you refused to comply with a preliminary test under s6 may also, in some cases, be used in court as evidence against you.
In conclusion, the police have a broad discretion to require a driver to co-operate with a preliminary test for alcohol or drugs. As it is an offence to refuse to comply, and you can still be taken for an evidential s7 test in the case of refusal, the cases in which it would be advisable to refuse to comply with a s6 preliminary test are very few in number.
A failure to follow procedure in the case of a s7 evidential test, however, is much more damaging to the prosecution case. In the case of R v S Mr S was caught drink driving, and provided samples of breath at both the roadside and at the police station. However, following advice from his Road Law Barrister, Mr S walked from court without a conviction – the crown decided to drop the case against him on the basis that the police did not follow the correct procedure when operating the breathalyser.
If you are arrested for drink driving, or would like advice in relation to any other road law case against you, please do not hesitate to contact us for your free consultation.
The contents of this article should not be relied upon in isolation. Each case is fact specific and this article should not be treated as legal advice or as a substitute for legal advice.
 DPP v Wilson  RTR 375
 See, generally, R v Sang  AC 402
 R v Downey  RTR 257
 R v Lennard  2 All ER 831