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Are the Police taking the Pee? (Literally)

April 01 2015

Forensic Science Interpreting The Evidence

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Alcohol & Drink Driving

As a physiological basis for analysing a person’s blood alcohol level, urine is far from ideal. It does not give a real time indication of alcohol level even when collected appropriately. When collected inappropriately, it is not fit for purpose. 

The analysis of alcohol in urine has been part of drink-drive legislation for over 50 years. Back in the 1960s the British Medical Association recommended to Parliament that for this purpose two specimens of urine should be collected, that these specimens be taken at least 30 minutes apart and that both specimens be analysed.  Unfortunately these recommendations were not translated into statute. Instead, today’s police procedure forms simply require a detainee to provide two urine specimens within one hour. The first is discarded, the second is retained for analysis. What is not clearly understood is why it is necessary to collect two samples in the first place.

The purpose of the first specimen is to clear the bladder of urine, since this contains alcohol that has been eliminated from the blood over an unknown period of time. The second specimen should then comprise urine that has been freshly formed in the bladder and it is this specimen which is approximately representative of a person’s blood alcohol level at the time of sampling. Emptying the bladder in the first sample is fundamental to the reliability of the second sample. But the police procedure forms do not explain this; they merely require the presiding officer to record the times at which the first and second specimens are provided. As a consequence, a multitude of misunderstandings arise from police station to court which stem from a lack of basic training, a poorly devised collection procedure and imprecise terminology:

1. POLICE TRAINING. Prior to a breath test detailed paragraphs must be read out loud and verbatim to a detainee; there are no similar requirements prior to the provision of urine specimens however, and police officers are not trained in the same manner as for breath testing. There is no explanation of the requirement for the provision of the two specimens, no detail to indicate that the detainee should try to empty their bladder with the first specimen and apparently no training given to officers as to what they are trying to achieve with the two specimen method. Nowhere is this lack of training more obvious than in the witness box, where Magistrates can be misled, albeit unwittingly, by police officers providing nonsensical explanations such as: two specimens are needed because it is necessary to reach "deep bladder urine, just like deep lung air" or, the purpose of the second specimen is to "reach the alcohol that floats on top of the water in the bladder"!  

2. NO EXPLANATION GIVEN TO DETAINEES.  Detainees may be told they must provide two urine specimens within an hour, or face a fail to provide charge. That is all they are told: two specimens or a criminal charge - that's fairly daunting. With no background knowledge, no understanding of biology or alcohol metabolism and on the basis of that information, a detainee might be forgiven for thinking, " I mustn’t give too much in the first specimen else I might not be able to go again within an hour". And in doing so, they inadvertently fail to empty their bladder with the first sample such that the second sample contains the same bladder content as the first.   

3. COLLECTION CUP SIZE MAY PREVENT BLADDER EMPTYING. A urine collection kit includes: a collection vessel and two sealable containers into which the second specimen is divided. The collection vessel used can be as small as 250-300ml or as large as one litre. Studies[1] have found median voided volumes of 330ml for women and 400ml for men. If the volume of the collection vessel is larger than the content of a detainee’s bladder, the first specimen may empty the bladder. But equally, if the volume of the vessel is smaller than the contents of a detainee’s bladder, the first specimen in that vessel will not empty the bladder. And without instructions on what to do with the rest of the bladder content, a detainee may well hang onto it. Often, as soon as the vessel is handed back, the detainee will provide a 'second' specimen but in fact it is just a continuation of the same bladder content as the first specimen. 

The complicating issue here is the concept of two specimens. In the above scenario, the detainee is confident he has provided two specimens and the officer is satisfied (because he has witnessed) that two specimens have been collected. But in fact the two specimens are from the same bladder pool and so whilst the procedure has been followed, the intended and critical purpose of the procedure has not been satisfied. 

4.  NO PROCEDURAL REQUIREMENT FOR A SPECIFIC TIME GAP BETWEEN SPECIMENS, FOR ANY VOLUME RECORDING, OR FOR THE BLADDER TO BE EMPTIED. Urine enters the bladder at a certain rate and so if the second specimen has a large volume but is given only a few minutes after the first, this is evidence of a bladder not being emptied by the first specimen. Wilkinson’s Road Traffic Offences is described as the definitive authority on road traffic offences in England and Wales, is heavily relied upon by courts and yet it is particularly unhelpful with regard to this issue. It states a fact, already obvious from police procedure forms, that there is no requirement recorded in the collection procedure for the first specimen to empty the bladder.  Because Wilkinson’s states this, magistrates apparently dare not draw any negative inference from evidence that shows a bladder has not been emptied by the first specimen. But this is the entire basis of the requirement for two specimens, it is the whole reason that the procedure was put together this way by parliament back in the '60s, it is the whole reason for police having to spend time waiting for two specimens rather than just analysing the first one. If the bladder has not been properly emptied, then a second specimen is merely a continuation of the first and therefore not fresh urine and therefore it does not provide a time-relevant alcohol level of the person providing that specimen. 

5. CASELAW. There is case law (albeit fairly aged) both for and against cases of this type. In Prosser-v-Dickeson [1982] RTR 96, the case was dismissed on the basis that there were only 2 minutes between specimens and the detainee did not re-dress, suggesting that the specimens were not different. In Over-v-Musker [1985] RTR 84, the magistrates also held that two specimens were not distinct when a detainee gave a second specimen only a minute after the first. An appeal by the prosecutor was upheld, however, on the basis that the detainee willingly provided the second specimen, (although if a defendant has no knowledge of the significance of this, that position is extremely difficult to reconcile with fairness). 

It is clear from my experience of magistrates’ comments in court that magistrates can see there are flaws in procedure; they understand that if the bladder is not empty when the second specimen is provided then the subsequent test result may be affected. Nevertheless, their decisions are hamstrung by:

a)    statute which makes no requirement for the first specimen to empty the bladder, despite this being absolutely critical to the reliability of the second specimen;

b)    case law which places the onus on an a detainee to comprehend procedure, even when that procedure is not adequately explained;

c)     procedure which does not specify a minimum time gap between the specimens, despite the BMA’s original recommendation of at least 30 minutes and despite the physiological evidence that a short time gap indicates an improperly-emptied bladder;

and, hence, magistrates feel they must convict.

It is bewildering that there are pages and pages devoted to breath tests in the police procedure forms and yet barely half a page on urine procedure. As a consequence of this failing, urine test procedures are misinterpreted, magistrates feel they are obliged to ignore evidence of inadequate sampling (because they have no mandate to do otherwise) and defendants are convicted on the basis of unreliable evidence.    



[1] Urology Nursing 2011; 31(3)


Jennefer Gray
BSc(Hons), MSc, TIFireE, MRSC

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