What happens if you are arrested for drink driving and are asked to provide an evidential specimen of breath, blood or urine for analysis?

In our previous article, we examined the law relating to preliminary testing in the drink driving context and established that preliminary tests are used to provide the police with a rough indication as to whether a driver is over the limit at the time of the test so that a decision can be made as to whether the driver should be arrested and taken for further testing.  In this article, we will look at what happens after the preliminary test returns a “positive” result.

Breath, blood or urine?

Whilst a preliminary test for drink driving typically involves breathing into a handheld breathalyser, under s7 Road Traffic Act 1988 (“RTA 1988”) the police may require the driver to provide two specimens of breath, or one specimen of blood or urine, for testing.

Section 7(3) RTA 1988 provides that the police must use breath testing unless this would be unsuitable or impracticable for one of the following reasons:

  1. The constable requiring a specimen has reasonable cause to believe that a specimen of breath should not be provided for medical reasons;
  2. Evidential specimens of breath have not been provided elsewhere and a suitable evidential breathalyser is unavailable;
  3. A suitable evidential breathalyser has already been used, but the constable has reasonable cause to believe that the readings were inaccurate; or
  4. The constable has reasonable cause to believe that the driver’s state is caused (if only in part) by drugs rather than alcohol.

As with the preliminary test, the request for a specimen can only be made in certain locations.  There does not, however, appear to be a restriction on where the specimen is actually taken providing the initial request is made in the right place.

Where the specimen is of breath, the request must be made at a police station, a hospital, or at (or near) a place where the preliminary breath test has been administered.[1]  Where the specimen requested is of blood or urine, the request can only be made at a police station or hospital.[2]

In cases where the police have a choice as to whether to request blood or urine (ie. in any case where breath is not appropriate for one of the reasons outlined above) it is for the constable making the request to decide which type of specimen to require.[3]  The only exception to this is where a doctor provides a medical opinion to the effect that blood would be inappropriate.[4]

What if the breathalyser result is borderline?

The general rule is that, of the two specimens of breath provided, the police will use the lower reading and will entirely disregard the higher one.[5]  However, if the lower specimen contains no more than 50 microgrammes of alcohol in 100ml of breath (the legal limit being 35 microgrammes) the driver is entitled to make a claim under s8(2) RTA 1988.  Making such a claim entitles the driver to provide a specimen of blood or urine for analysis which will be used instead of the breathalyser results (noting, of course, that it is for the constable to elect between urine and blood)[6].

Importantly, if the result is borderline and the police fail to inform the driver of their right to provide an alternative sample under s8 RTA 1988 in a manner which is clear enough to give the driver enough information to make an informed decision, in the majority of cases this will be sufficient to overturn any conviction resulting from the investigation.[7]

What if I don’t want to provide a specimen?

Before obtaining a specimen pursuant to section 7 RTA 1988, the police must provide the driver with a warning that a failure to provide a specimen of breath, blood or urine in circumstances where it is validly required is an offence and may render the driver liable to prosecution.

In terms of sentencing, this offence is very similar to the actual drink driving offences in that a failure to provide will generally result in a disqualification.  This offence was clearly created to encourage people to comply with the evidential testing procedure: if you will be disqualified for failing to provide a specimen, and are likely to be disqualified if you do provide a specimen and are found to be over the limit, then there is no advantage to refusing to provide a specimen.

It should, however, be noted that the police cannot force you to provide a specimen of any description without your consent, unless s7A RTA 1988 applies.  Section 7A has a very narrow application and is generally restricted to cases where the driver is incapable of providing consent for medical reasons.  Examples of when s7A applies could include cases where the driver has a previously existing condition (ie. dementia) and is unable to consent for that reason, or where the driver was involved in a serious collision and is unable to consent due to being in a coma.  In such cases, a doctor can take a blood sample from the driver.  However, the sample cannot be tested in a laboratory until the driver provides his consent.[8]  Failure to provide such consent is, as would be anticipated, also an offence.[9]


It will come as no surprise that this article is only the tip of the iceberg.  There are many more technical rules surrounding evidential specimens which could help you avoid a conviction, which is why you should not hesitate to contact us for your free consultation if you face a prosecution for drink driving.  Our Road Law Barristers are very familiar with the technicalities surrounding drink driving and, with our expertise on your side, you could retain your licence and your livelihood.

One of our previous clients, Mr S, faced the prospect of disqualification after being arrested for drink driving and providing positive breath samples both at the roadside and at the police station.[10]  However, after examining the procedure followed by the police in his case, it emerged that the breath samples were improperly obtained.  Our barristers constructed a legal argument to challenge the admissibility of the breathalyser evidence, and as a result the CPS decided to drop the case.


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.

[1] s7(2) RTA 1988

[2] s7(3) RTA 1988

[3] s7(4) RTA 1988

[4] s7(4A) RTA 1988

[5] s8 RTA 1988

[6] s7(4) RTA 1988

[7] Clwyd Justices, ex p Charles (1990) 154 JP 486

[8] s7A(4) RTA 1988

[9] s7A(5) RTA 1988

[10] https://www.roadlawbarristers.co.uk/about-us/case-studies/

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