Section 4, Road Traffic Act 1988

It is an offence to drive or attempt to drive a motor vehicle whist unfit through drugs.   A person is unfit if their ability to drive is impaired as a consequence of taking drugs.  The impairment can be brought about from use of illegal drugs, legal highs and even prescription medication taken legitimately.  It also includes any other substance that causes impairment to a person's ability to drive.


The penalties for driving or attempting to drive whilst under the influence of drugs are similar to those of drink driving and include:

  • A fine of up to £5000; and
  • A minimum 12 month period of disqualification. 
  • For serious contraventions of this offence a community based disposal or imprisonment can also be imposed.  

Drug Driving Charges

A charge for driving whilst under the influence of drugs will usually arise because the police have reason to believe that your driving was impaired as a direct result of consuming drugs.  The law in this area allows the police to bring a charge in circumstances where an exact measurement of drugs in a person’s system cannot be made. 

This type of offence frequently comes to light following an accident or where the police have stopped someone because of the manner of driving.  These particular factors may also ultimately support the contention that the driver was under the influence of something or other.

Testing For Drugs

At present there is no universal device that can quickly determine if a driver has drugs, other than cannabis, in his system.  If the police think drugs have been taken the usual practice is to carry out a “Field Impairment Test”.  This requires a driver to perform a series of basic tests that might include simple balancing and counting exercises.

If, following these tests, the police have reasonable grounds to believe that you are unfit to drive because of drugs you will be arrested, taken to a police office and required to provide a sample of blood or urine.  The same requirement can be made if you are subsequently examined by a doctor who is of the opinion that you are under the influence of drugs.  A refusal or failure to provide such a sample is a separate offence of Failing to Provide a Specimen for Analysis.

The requirement for a blood or urine sample can also be made even where the driver has already provided two specimens of breath at a police office which are negative or below the legal limit of alcohol.  This might happen if the police initially thought that someone was under the influence of alcohol, rather than drugs or both.  If a sample of blood or urine is provided it will be sent to a forensic scientist for analysis to determine if any drug is present.  This usually takes a few weeks.

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Prosecuting Drug Driving Cases

In all cases the prosecution must prove, beyond a reasonable doubt, that:

  • The driver was unfit through drugs; and
  • His driving was impaired

The prosecution must also prove that the police carried out all the procedures laid down by law.  Mistakes in the procedures may prove fatal and provide a defence to charges under this section.

Drug Driving Defences

The presence of drugs in your system does not automatically mean that a conviction will follow.  The prosecution must establish that the drug in question has impaired your ability to drive in some way.  This would be an area of focus for the defence to demonstrate that even where drugs have been taken this did not impair the ability to drive. 

In some circumstances the defence may also present arguments that amount to what are called “Special Reasons”.  If Special Reasons are successfully made out before the court the penalties may be reduced and disqualification may be avoided altogether.  An example of Special Reasons in this type of case is where someone has been prescribed medication and is not aware of the effects this may have if taken with other medicines or a small amount of alcohol. 

How we can help

As specialist road traffic lawyers we are best placed to give you the right advice. The law relating to drug and alcohol related offences is technical and complex. Our experience and expertise in this area will quickly determine the merits of the case and the best option for you. If there is no defence or the prospects of success are low we will tell you so and concentrate on damage limitation. We pride ourselves in offering a service that is friendly, reliable and honest. For free advice that is without pressure or obligation simply contact us:

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