In drink drive cases where defendants are requested to provide urine samples it is evident that the required procedure is open to unwitting misinterpretation. A urine sample may be provided in cases where a breath specimen is being replaced or if a breath specimen cannot be provided. In these cases The (revised) Road Traffic Act 1988 Section 7(5) states:
"A specimen of urine shall be provided within one hour of the requirement for its provision being made and after the provision of a previous specimen of urine."
In other words, a detainee must provide two samples of urine within one hour. So why two samples? Excretion of alcohol from the body via urine allows a person’s alcohol level to be determined by analysis of a urine sample. However, because urine collects in the bladder over a period of time, the alcohol concentration of a urine sample does not indicate a person’s alcohol level at the time the sample is provided, but rather it indicates the person’s average alcohol level during the time period over which the urine collected in the bladder (i.e. since the time the bladder was last emptied).
In a drink drive procedure, the purpose of the first sample of urine is to completely empty the bladder. This sample is discarded. Once the bladder is empty, the second urine sample has to be provided within one hour of the requirement being made. New urine that collects in the bladder over this time period will represent the detainee’s average alcohol concentration between the time of the first and second specimens being provided.
Police station procedure forms completed contemporaneously require the times of both specimens to be recorded. In several recent cases seen at KBC, the first and second specimen times are separated by a single minute! Such a short period does not allow sufficient time for the bladder to refill and so the ‘second’ specimen actually must be just a later part of the first specimen. If this is correct the urine sample will not reflect the true alcohol level of the person at the time of sampling and may be an over (or under) estimation of that person’s actual alcohol level at that time.
There is a subtle but important difference between providing two urine specimens and providing two distinct urine specimens. In both scenarios, the police officer in charge can have followed the procedure correctly by disposing of the ‘first’ specimen and retaining the ‘second’. However, in cases where only a few minutes separate the two specimens, and it cannot be established in any other way that the second specimen was distinct from the first, then the reliability of the test result will be in doubt.
Jenny Gray, Keith Borer Consultants