You may be surprised to know that you cannot be given the automatic option of providing a blood test at the police station, even if you ask for it. A blood specimen can only be provided in the following circumstances;
The police cannot charge you with drink driving before the results of the blood specimen have been obtained, even if your roadside reading was high. This means you could remain on police bail for two weeks or more. You can continue to drive over this period, unless the police tell you otherwise.
During this time the police will send your sample to an independent laboratory, who will analyse the sample for alcohol. Because the laboratories used by the police are independent, they often have a very quick ‘turn around’ time (perhaps 2 days). This means that any delay in the returning of the results probably occurred at the police’s end.
Due to it becoming common practice amongst police stations to leave blood samples lying around, the government commissioned an investigation by the HM Inspectorate. The report that was produced advised that forensic samples be processed onwards within one week of being taken.
The report, however, seems not to have reached the police, as it is now more common for samples to remain at police stations for up to 3 weeks before being sent to the laboratory.
The issue here is that blood is an organic material and will decompose overtime. A result of this is that alcohol is created in the blood (a process known as fermentation). Each time a refrigerator door is opened, the temperature inside the fridge will fluctuate. This can disturb the stability of the specimen and may speed up the fermentation process.
One way to prevent this from happening is to add a preservative to the sample, such a sodium fluoride. Often, due to lack of training, officers fail to ensure that this preservative is evenly distributed within the vial, or added at all. The result here is that the sample finally analysed by the laboratory contains a higher alcohol concentration than what was in your body at the time it was taken (perhaps enough to place you over the limit).
If your sample is above the prescribed limit for blood, you will be charged and bailed to court. The first court hearing is particularly important, as it is the first opportunity we will have to consider the evidence against you and enter a plea with the court.
On this date the CPS should provide a report detailing the analysis of your blood sample, known as the MG22(b) or ‘Streamlined Forensic Toxicology Report’. This report should contain all the relevant technical information that I would need to check, including:
Any inconsistencies or discrepancies with the report would quickly be highlighted to the prosecutor, who may agree immediately to drop the case (if there is no realistic prospect of a conviction). Alternatively, we may decide to keep the issue quiet and raise it at a later date when it would do more damage to the CPS’s case.
The difference with blood is that there is no room for error or interpretation. If, for example, a sample had clotted before being analysed, then the report will highlight this and it cannot be challenged otherwise.