Forensic Science Experts for Criminal Defence Solicitors

Call head office 01782 394929
London Office 0207 118 9001
Freephone 0800 999 7 666
Drink Driving

Drink Driving

Drink Driving


There are thousands of types of alcohol. However, the one which we consume as ‘alcohol’ is called Ethanol.

The Ethanol molecule is a specific shape. It is precision-engineered by nature to affect your brain when swept into your bloodstream. This is because the Ethanol molecule is water-soluble, allowing this fast absorption. It is also fat-soluble, meaning Ethanol can also pass through cell membranes.


Difference between Absorption and Elimination

Absorption is the rate at which alcohol is absorbed into the bloodstream via the stomach and small intestine.

  • Does not differ depending on age, sex, and weight.

  • But does differ depending on the amount of food in the stomach

  • It does differ depending on the type of alcohol ingested.

E.g. absorption would be much quicker for a gin & lemonade, as opposed to a pint of ale.

Elimination is the rate at which alcohol is broken down/ or eliminated from the blood (or breath and urine.)


Consumption and Concentration

When considering absorption and elimination, we must consider consumption. With the consumption rate, we are provided with a concentration. Specifically the concentration of alcohol in a person’s system.

The pattern of alcohol consumption is important. Drinking two pints of lager in 30 minutes is different from drinking the same amount in 2 hours. So, the concentration of alcohol in a person’s systems is dependent on their height, weight, and sex.

E.g. There is a man and a woman. Both are the exact same height and weight. They both drink the same amount of alcohol, at the same time. But due to the naturally higher occurring fat levels found in females, the concentration of alcohol in the female would be higher.


The battle between Absorption and Elimination

It takes up to an hour for any consumed alcohol to be absorbed into a person’s bloodstream. During this time, it is a biological battle between absorption and elimination. However, after approximately an hour of consuming any alcohol, a person will enter the elimination phase only. Thus the alcohol concentration of a person is only decreasing. A person’s body can only eliminate alcohol at a certain rate, which does not increase with the amount of alcohol consumed.


Legislation for Drink Driving

There has been legislation for drink driving since 1872. But, in modern times, motorists have been prosecuted under the Road Traffic Act 1988.

The first consideration of using blood, breath, or urine for analysis was 1964. In which the US study suggested that the chance of an accident sharply increases when alcohol (ethanol) exceeds 80 milligrammes per 100ml of blood. Following this, the 1967 Road Safety Act introduced the 80 mg% limit (107 mg% in urine).


In 1968 the first ‘roadside’ or portable breathalyser was introduced. 

Later in 1981, the Transport Act saw the introduction of evidential breath testing. With a legal limit set at 35 microgrammes per 100ml of breath (35ug%). This figure was derived from data that shows breath reading at a given blood alcohol concentration. 2300 more alcohol in 100ml of blood compared to 100ml of breath.

The first evidential breath testing instrument was introduced in 1983: the Lion Intoxilyzer 3000. Later on, extra testing instruments were introduced; Intoximeter and Camic Datamaster.


Bericon: Our experience with Drink Driving cases 

At Bericon Forensics, we have over 35 years of experience in drinking driving calculation cases. Our offering includes expert and speedy reports for both legal professionals and members of the public. Often turning around reports within days. 


Common questions we are asking in drink driving cases:

  • Would a medical condition affect the elimination of alcohol? 
  • Would my medication affect my absorption of alcohol?
  • Would a medical condition such as asthma affect the ability to provide a breath sample? (In ‘failure to provide’ cases) 
  • Would prescribed medication such as Night Nurse or anti-depressants affect a reading?
  • Would my medication affect the reliability of the breath testing machines?


Common responses from individuals in drink driving cases:

  • I felt OK to drive 
  • I only drove 200 yards 
  • I can't believe I was over the limit 
  • I’ve only had 2 pints 
  • The machine isn’t working 
  • I’m taking painkillers, antidepressants…
  • I didn't understand the instructions
  • I blew as hard as I could 


Common defences for drink driving cases:

In a case of Excess Alcohol or driving with Excess Alcohol (Road Traffic Act 1988), a statutory defence would include the consumption of ‘laced’ or ‘spiked’ drinks. This refers to the unknowing consumption of alcohol. Where there has been the addition of alcohol to a person’s drinks, causing them to exceed the legal limit for driving. 

An additional defence, is referred to as the ‘hip-flask’ or post-driving drinking defence. This refers to the consumption of alcohol after having driven, and before the arrival of police officers. Often consumed in the aftermath of an accident. The declaration of post-driving consumption should invoke the MGDD/D procedure. Which asks the individual to report what alcohol they have consumed and when. Calculations can be undertaken relating to ‘drunk in charge’ cases. Where data is required to state when an individual would have been under the statutory limit to drive. 

To discuss drink driving cases, and or interpretation of results, please contact us.

Get a Quote Today

    [sharethis]Share this page

    Get a Quote Today