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Drink Driving Defences

Drink Driving law is a complex subject which gives rise to a large number of possible defences ranging from factual defences which can be as simple as, “I wasn’t driving”, to technical arguments surrounding the operation of evidential breath testing equipment. As specialists in drink driving law, we have an extensive understanding of these defences and pride ourselves on our ability to both identify and successfully argue these defences. If you have a defence we will find it.

Given the consequences of a conviction, particularly the imposition of a long period of disqualification (usually between 12 and 36 months), the benefit of identifying a defence which may avoid your disqualification is significant. In some cases the defence will be clear from the outset and we will be able to advise you of this, in others we may need to carry out further investigations in order to identify whether a particular defence is available. For example, you may think that the police had failed to warn you that you may be prosecuted if you fail to provide a specimen. If this is true, you will have an absolute defence and therefore we would seek to obtain cctv footage from the police station covering the breath testing procedure, in order to establish whether or not your recollection is correct.

When you contact us, we will provide you with an initial assessment of your case and will identify to you the defence(s) which may be applicable to your case. We will also give you an honest appraisal of your case and the prospects of success.

Below we have prepared a comprehensive list of the types of defences which are applicable to drink driving cases and may apply to the facts of your case. Some of these defences are of a general nature and apply to all cases, whilst others are specific to individual offences:


Factual Drink Driving Defences

  • I was not driving or attempting to drive
  • I was not driving a mechanically propelled vehicle
  • The location of the offence was not a road or other public place
  • I was acting in necessity or under “duress of circumstance” – This requires a person to fear serious harm and harm and his response must be what could be expected of a person of reasonable firmness.

Post Alcohol Consumption or “Hip Flask” Defence

If you are not stopped by the police whilst driving, it may be that between the time of your driving and providing an evidential specimen of breath/urine/blood sample, that you have consumed alcohol.

If this is the case then will have a defence if it can be argued that had it not been for your post driving consumption (alcohol consumed after driving) then your evidential specimen of breath/blood/urine would have been below the legal prescribed limit at the time of driving.

In arguing this defence we will need to instruct one of our experts to provide a “back calculation” report, which will provide evidence of what your breath/blood/urine specimen would have been at the time of driving.

If it is shown that it is your post driving consumption that has caused you to exceed the specified limit, then you will be found not guilty of the offence.

Procedural Errors in Obtaining a Specimen

In order for the prosecution to rely upon any specimen of breath/blood/urine to prove that the proportion of alcohol in your breath was above the “prescribed limit”, that evidence must be admissible. There are a number of ways in which the police may make errors in the taking of such specimens and which may then allow us to have that evidence excluded, such that you are acquitted of the offence. These are detailed below:

Statutory warning

In order for a specimen to be relied upon, the police must warn you that if you fail to provide a specimen you may be prosecuted. This is known as the “statutory warning. If this warning is not given, then you are entitled to be acquitted even in circumstances where you have provided a positive specimen.

If you are unsure of whether this warning was given we will obtain a copy of the cctv footage from the police station, in order to establish whether or not this warning was given.

Entitlement to provide a secondary specimen of blood or urine

If having provided two specimens of breath at the police station, the lower of these two specimens is 50mg (alcohol)/100ml of breath or below, then you are entitled to be offered to provide a replacement specimen of either blood or urine (to be decided by the officer).

If this option is not explained or you accept this offer and then are not allowed the opportunity to provide the specimen then your specimens of breath will be inadmissible and you will be acquitted of the offence.

Taking of blood samples

A blood sample must be taken by a medical practitioner or a registered health care professional (i.e. nurse), you must also give consent for the specimen to be taken.

If either of these things are not done, the specimen will be inadmissible and you will be acquitted of the offence.

Taking of urine samples

Two specimens of urine must be taken within one hour of one another. If however, there is insufficient time between specimens or one specimen is split into two, this specimen will not be admissible and you will be acquitted of the offence.

Failure to offer sample of blood or urine

A person who provides a specimen of blood or urine is entitled to be told of his right to part of that sample. This allows a person who wishes to do so, to have their part of the specimen independently tested.

If the police fail to provide you with part of your sample when requested or do not inform you of this right, you may be acquitted of the offence.

Continuity of blood and urine specimens

Where the prosecution relies on a blood or urine specimen to prove its case, the defence may put the prosecution to strict proof to prove that the specimen for which a certificate is given providing the laboratory result is the same specimen which was given at the police station. The prosecution is called to prove the “continuity” of its evidence, such that they can demonstrate every hand through which the specimen has passed.

If the prosecution is unable to prove continuity, this may lead to your acquittal for the offence.

Reliability of Evidential Breath Testing Equipment

In prosecuting a person for a “drink driving” offence (with the exception of driving whilst unfit), the prosecution will most often rely on evidence provided of the proportion of alcohol in a persons breath. The prosecution provide evidence of this by way of a print out provided by a breath testing device which has been approved for use by the Secretary of State. The devices most commonly in use for this purpose are the CAMIC Datamaster, the Intoximeter EC/IR and the Lon Intoxilyser 6000UK.

Whilst these devices are Type Approved and accordingly tested, in those cases where you do not believe the quantity of alcohol you have consumed is consistent with the breath alcohol reading provided, we can investigate and challenge the reliability of the equipment used. This can include:

  • Reviewing the printout produced by the machine to determine whether it has operated correctly
  • Obtaining the calibration and maintenance records for the machine in order to establish whether it has been properly maintained
  • Establishing whether the equipment used has been modified in any way such that it is no longer “type approved” and its evidence is inadmissible

Specific Defences:

Failing to provide a specimen

The offence of failing to provide a specimen includes provision that this should be without “reasonable excuse”. If a reasonable excuse is raised for not providing a specimen then you should be acquitted of the offence unless the prosecution can prove (beyond reasonable doubt) that no reasonable excuse existed.

A reasonable excuse will generally be one which prevents a person from physically or mentally being unable to provide it.

Specimens of Breath

Most “reasonable excuses” centre around a persons failure to provide an evidential specimen of breath at the police station. In such circumstances, if a person is unable to provide a sufficient flow of breath into the machine such that it registers a specimen of breath, then no specimen will be provided and this will be considered as a fail and the person will be prosecuted for the offence of failing to provide a specimen. If however, a person can show that there is a genuine physical or mental reason as to why they were unable to provide a specimen and this is accepted as “reasonable” then they will be acquitted. Examples of the types of reasons why a person may not be able to provide a breath specimen include:

  • Asthma
  • Chest Infection
  • Long term smoker
  • Small lung capacity
  • Physical position when giving the specimen
  • Anxiety and panic attacks

In order to support any argument that a medical condition caused you to be unable to provide a specimen, we would in all cases seek to obtain a report from one of our experts explaining why your physical or mental condition prevented you from providing a specimen.

If it is simply the case that you know you tried your hardest yet were still unable to provide a specimen, we can arrange for you to visit one of our experts and undergo a simulation of the breath testing procedure on a similar machine in order to identify any problems which you may have.

Specimens of blood or urine

As with specimens of breath, there may be physical or mental reasons why a person is unable to provide a specimen of blood or urine, these can include:

  • Fear or phobia of needles
  • Prostate problems

Expert medical evidence should be obtained to support any such reasonable excuse.

Being Drunk In Charge of a Motor Vehicle

If it is alleged that you were “in charge” of a motor vehicle whilst the proportion of alcohol in your breath/blood/urine was above the prescribed limit or you were “unfit”, then you will have a defence if you can show that there was no likelihood of you driving your vehicle whilst you remained in excess of the prescribed limit or unfit.

This type of defence will often present itself where a person decides to sleep in their car after a night out or after finding themselves unexpectedly without a place to sleep. In these circumstances whilst you may be in charge of the vehicle and may even have switched the engine on to get warm, you will be acquitted of the offence if you can show (the burden of proof is on the defence) that you would not have driven the vehicle whilst still over the limit.

In order to prove this defence, expert evidence will be required addressing your breath/blood/urine reading (or unfitness) and the rate at which you would have eliminated (metabolised) alcohol, so as to establish at what point in the future you would have been fit to drive. By way of example if you had consumed alcohol up to 12pm and then slept in your car with the intention of driving when you woke at 7am, a report would be required showing that by 7am the proportion of alcohol in your system would have been below the prescribed limit.