Driving whilst under the influence of alcohol or drugs

Driving over the Limit: Alcohol

There are two main offences that concern excess alcohol driving both provided for in the Road Traffic Act 1988:

• Driving, or being in charge of a motor vehicle, when under the influence of drink (section 4); and
• Driving, or being in charge of a motor vehicle, with alcohol concentration above the prescribed limit (section 5).

The first of these offences (section 4) is the less commonly charged as most cases where the offence may apply can be suitably charged under the more definite section 5. As is shown below, this is largely due to the broader, more evidentially onerous, nature of section 4.

The Offences

Driving under the Influence

There are two offences under section 4: driving or attempting to drive when under the influence of drink, and being in charge of a vehicle when under the influence of drink. If charged under section 4, therefore, the Prosecution will need to prove that:

1. You were driving or attempting to drive a vehicle; or
2. Were in charge of a vehicle on the road; and
3. You had consumed alcohol which was still in your system; and
4. The alcohol rendered you unfit to drive.

Case law provides flesh to some of these terms:

In charge – A question of fact dependent on the circumstances, to be determined on a case-by-case basis. A person is deemed to be in charge of a vehicle until he hands that charge on to someone else.

Attempts to drive – That steps have been taken to drive the vehicle, beyond the merely preparatory stage, which are a part of the actual process of causing the vehicle to move.

Unfit to drive – When proper control of the vehicle is impaired. This is again fact-dependent, but may be demonstrated through behaviour or the provision of a specimen. Expert medical evidence may be given to determine the question of impairment.

However, there will be a defence to the charge where it is proved that there was no likelihood of actually driving when you were unfit to drive through drink.

A charge under section 4 will therefore be heavily dependent on the circumstances of the case, and will need to be shown to prove that an individual was not only in drink, but also unfit to drive.

Driving when above the Limit

An offence under section 5 is similar to driving under the influence, with the addition that it is strictly based on whether the alcohol measured exceeds the prescribed limit. As such, the Prosecution would need to prove that:

1. You were driving or attempting to drive a vehicle; or
2. Were in charge of a vehicle on the road; and
3. The level of alcohol in your system exceeded the prescribed limit.

The limits are set by statute, and a specimen must be taken so that the concentration of alcohol can be measured. The specimen can be either breath, blood or urine (breath is the most usual). The limits are as follows:

• 35 microgrammes of alcohol in 100 millilitres of breath
• 80 milligrammes of alcohol in 100 millilitres of blood
• 107 milligrammes of alcohol in 100 millilitres of urine

In practice, however, prosecutions are not brought unless the reading is at 40 microgrammes or more (when measuring breath with an intoximeter).

A constable is required to take two samples of breath, and the lower reading is the one that is used for the purposes of any prosecution. Failure to provide a specimen when requested is also an offence under section 7(6) of the Road Traffic Act 1988.

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Driving over the Limit: Drugs

The Offences

Drug driving offences are provided for under section 5A of the Road Traffic Act 1988. They are:

• Driving or attempting to drive a motor vehicle on a road or public place when there is a controlled drug in your body that exceeds the specified limit for that drug;
• Being in charge of a motor vehicle on a road or public place when there is a controlled drug in your body that exceeds the specified limit for that drug.

Definitions

Attempting to drive: Steps have been taken to drive the vehicle, beyond the merely preparatory stage, which are a part of the actual process of causing the vehicle to move.

Being in charge: A question of fact dependent on the circumstances, to be determined on a case-by-case basis. A person is deemed to be in charge of a vehicle until he hands that charge on to someone else.

Controlled drug: A drug as defined for the purposes of the Misuse of Drugs Act 1971.

Specified limit: The controlled drugs and their specified limits are listed in the Drug Driving (Specified Limits) (England and Wales) Regulations 2014 (as amended). The limits are given in terms of microgrammes per litre of blood (please see the table at the bottom of this article for the full list and the corresponding limits).

Defences

It is defence to show that the drug was prescribed by a doctor, taken in accordance with any relevant instructions or guidance, and the possession of the drug was not unlawful under the Misuse of Drugs Act at the time of taking it.

It is also a defence to show that at the time of the alleged offending there was no likelihood of the defendant actually driving whilst the drug was in his body and above the specified limit.

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