Drink Driving Offences

Legal Guidance, Driving offences


This guidance defines the evidential considerations when reviewing drink driving cases and draws attention to the requirement to carefully consider the statutory procedure to be followed by the police.

Evidential Considerations

When reviewing any drink/driving case pay careful attention to the statutory procedures followed by the police. The considerations which follow deal only with the points which arise most frequently.

Post Driving Consumption and Back Calculations

If a driver claims that the proportion of alcohol in a breath or laboratory specimen provided by him is above the legal limit because he had consumed alcohol after he had ceased to drive, he will need to rebut the presumption contained in section 15(2) Road Traffic Offenders Act 1988 that the proportion of alcohol in his breath, blood or urine at the time of the alleged offence was not less than in the specimen. The presumption will be rebutted if the driver proves the matters set out at section 15(3) on a balance of probabilities. In order to do so he will usually rely upon expert scientific evidence to establish that his alleged post driving consumption of alcohol accounts for the excess found in his sample, which took him over the legal limit.

However, in (Dawson v Lunn [1986] RTR 234) it was held that the decision in (Pugsley v Hunter [1973] RTR 284), the leading authority on 'laced drinks', was equally applicable to this defence. Hence, the defence must call medical or scientific evidence on the point unless it is obvious to a layperson that the post offence consumption of alcohol explained the excess. Experience has shown that this is frequently argued in cases where the defendant claims to have consumed no alcohol prior to driving. Even here it will not be 'obvious' where the quantity of alcohol subsequently consumed is not consistent with the measured breath, blood or urine sample.

Conversely, if a driver provides a specimen some hours after the time of the alleged offence which is below the legal limit the Forensic Science Service (FSS), or a private laboratory, may advise that by means of back calculations based upon rates at which the human body eliminates alcohol it is possible to establish that the driver was in excess of the legal limit when the offence occurred. You are entitled to rely upon such back calculations for the purposes of proving an offence under section 5 - see (Gumbley v Cunningham (1989) 1 All ER 5) - but only if that evidence is easily understood and clearly persuasive of the presence of excess alcohol at the time of the alleged offence.

Expert evidence on post driving consumption

In either event, whether you are seeking to negative the driver's defence of post-driving consumption or prove that he was originally over the limit when the offence occurred, you will need to rely on expert evidence from the FSS which will include evidence of mathematical calculations based upon the elimination of alcohol within the driver's body over a period of time. Your chances of success will be increased if the evidence provided by the FSS relates as closely as possible to the physical characteristics of the driver and his consumption of both food and drink over the relevant period.

Information Required by the Expert

This information will normally be recorded by the officer on the Form MG/DD/D at the police station. However if the defence is not raised until a later time the FSS should be provided with as much information as can be obtained from the case papers and the officer in the case. The following information is relevant, where available:

  • the weight, height, build, age and sex of the driver; 
  • details of any food consumed from six hours before the offence and the provision of a breath or laboratory specimen; 
  • any known medical condition; 
  • details of any medication taken regularly, or within 4 hours prior to drinking; 
  • the type and quantity of alcohol consumed before the offence and, if possible, the times at which individual units of alcohol were consumed; 
  • the same information concerning any alcohol allegedly consumed after the offence but before the provision of a breath or laboratory specimen.

Failing to Provide a Specimen

If "reasonable excuse" is raised as a defence based on medical evidence you should require the defence to provide that evidence before the hearing, or seek an adjournment for that purpose. The matter can then be investigated and, if necessary, expert medical evidence obtained which addresses the specific issues raised by the defence. In (DPP v Crofton (1994) RTR 265) it was held that the court should consider the following matters in such circumstances: 

  • medical evidence of physical or mental inability to provide the specimen; 
  • the causative link between the physical or mental condition and the failure to provide the specimen.

Once such a defence is raised, the onus is upon the prosecution to negate it.

Procedures for Requests for Blood or Urine Samples at Police Stations

Sections 7, 8 and 9 of the Road Traffic Act 1988 (Stones 7-1378, 1379, 1379A) set out procedures which must be followed by the police when samples of blood or urine (laboratory samples) are taken. The admissibility of those specimens in excess alcohol cases depends upon the procedures being followed correctly. The defence have subjected those procedures to challenge on numerous occasions. You should note the following points in particular.

An obligatory requirement to provide a laboratory sample arises when one of the four reasons set out at section 7(3) occurs. Before such a sample is taken the driver needs to be provided with certain information by the officer, as follows: 

  • he must tell the driver the statutory reason under section 7(3) why breath specimens cannot be taken or used; 
  • he should tell the driver that in those circumstances he is required to give a sample of blood or urine, but that the officer will decide which; 
  • he must warn the driver that a failure to provide the sample required may result in prosecution; 
  • and if he has asked for a sample of blood, 
  • he should ask the driver if there is any medical reason why a specimen cannot or should not be taken by a doctor.

When, in the circumstances set out at section 8(2), a driver may choose to replace a breath specimen by supplying a laboratory sample,

The officer should inform the driver of the nature of the option open to him and what will be involved if he exercises it; 

  • he must inform the driver that the specimen of breath which he has given containing the lower proportion of alcohol exceeds the statutory limit; but does not exceed 50 microgrammes of alcohol in 100 millilitres of breath; 
  • he should inform the driver that in the circumstances he is entitled to claim to have this specimen replaced by a specimen of blood or urine if he wishes; but that, if he does so, it will be for the constable to decide whether the replacement specimen is to be of blood or urine and that if the officer requires a sample of blood, it will be taken by a doctor unless the doctor considers that there are medical reasons for taking blood, when urine may be given instead; 
  • he should ask the driver if there are any medical reasons why a sample of blood cannot or should not be taken from him by a doctor.

In relation to the taking of a laboratory sample in either of the above circumstances you must check that the officer has covered each of these points. The second is mandatory, so if the officer has failed to inform the driver of it he will be acquitted of the relevant allegation. It should thus be discontinued for lack of sufficient evidence. If any of the other points have been omitted the test is whether that omission deprived the driver of the opportunity to exercise the option, or caused him to exercise it in a way which he would not have done if that omission had not occurred. If the answer is in the negative then the omission by the officer should not be a reason for an acquittal. See DPP v Warren (1992) 4 All ER 865 and DPP v Jackson (1998) 3 All ER 769.

Doctor's advice to Constable re influence of drugs under s.7(3)(c) RTA 1988

Under section 7(3)(c) a constable may require a driver to provide a laboratory specimen when he has been advised by a medical practitioner that the condition of the driver might be due to some drug. The purpose of this provision is neither to prove that the driver is, or that the doctor believes him to be, under the influence of drugs - but simply to advise that the driver's condition might be due to some drug.

The doctor is not prohibited by the words of that statute from taking into account any fact or matter which he feels to be relevant. He is not restricted to considering the condition of the driver at the time of his examination. Officers are now frequently testing for driver impairment due to drugs at the road side. The tests are based primarily on the physical response of the driver to certain tasks. The doctor may consider the results of such tests when he advises a constable under section 7(3)(c).

Requests for Blood or Urine Samples at Hospital

When a driver is at a hospital as a patient he cannot be required to provide a breath sample and the conditions contained in section 9 (Stones 7-1379A) regarding medical consent must be complied with before he is required to provide a laboratory sample. Furthermore, the investigating officer must ask the driver if there is any reason why a specimen of blood should not be taken. The correct procedure is detailed in the MG/DD/C.

Challenging the evidential breath testing instrument

The first generation of Evidential Breath Testing Instruments (EBTIs) were replaced in 1999. All forces are now equipped with the Intoximeter EC/IR, the Camic Datamaster or the Lion Intoxylizer 6000UK. They detect and record a wider range of information when analysing breath samples

These three makes of instrument are a type approved by the Secretary of State for the purposes of the Road Traffic Act. Any challenge of that type approval must be made by way of an application for Judicial Review, not in the course of a summary trial relating to the performance of a particular instrument: (see DPP v Brown and DPP v Teixeira [2001] EWHC Admin 932, 166 JP 1)

In the case of a breath specimen there is a statutory assumption at section 15 RTA that the instrument concerned performed reliably. However, that assumption may be challenged by evidence relevant to the circumstances of that particular case. In order to convict in the face of such evidence the court must remain satisfied that the instrument provided a reading upon which they can rely. See (Cracknell v Willis (1998) 1AC 450 at 467), and (DPP v Brown; DPP v Teixeira)

The repeal of Section 69 Police and Criminal Evidence Act 1984

The EBTIs are computers. The provisions contained in section 69 PACE will no longer apply to prosecutions relating to incidents which occurred after 13 April 2000. Following the repeal of section 69 PACE, the admissibility of computer evidence will be governed by the position at common law. This means that there will be a presumption that the computer producing the document was working properly at the material time and that the record is admissible as real evidence.

That presumption can be rebutted if evidence to the contrary is adduced. In that event it will be for the party seeking to produce the computer record in evidence to satisfy the court that the computer was working properly at the material time.

Public Interest Considerations

There is a very clear public interest in preventing, detecting and prosecuting those who drink to excess and then drive. This is due to the clear danger posed to life, limb and property by such behaviour.

Where the defendant has driven a motor vehicle and the evidence is sufficient to support a charge under either section 4, 5 or 7(6), a prosecution will almost invariably follow.

For those who attempt to drive, or who are in charge of a vehicle, following excess consumption of alcohol there is similarly a clear public interest in prosecuting.

Offences contrary to sections 6(4) and 7(6) may be committed whether or not the defendant has been driving, attempting to drive or in charge of a vehicle. Where you are satisfied that the defendant has done none of those acts there is a greater degree of discretion as to whether proceedings are appropriate. However, particularly where an offence under section 7(6) is involved, a prosecution will normally be in the public interest.

Back Calculations - public interest

When considering a request from the police that back calculations be made, or reviewing a case based upon such evidence, (see also back calculations, above in this section) you should consider whether such a prosecution would be in the public interest. Factors to consider in the context of such a case in favour of prosecution might include: 

  • where a considerable lapse of time occurred between the incident of driving and the driver's arrest because of the driver's own culpable actions by, for example, absconding from the scene of an accident; 
  • where there are clear grounds for believing the driver to be a danger to other road users, such as the possession of previous drink/drive convictions; 
  • where there are other aggravating features, such as the fact that the driver was disqualified from driving or serious injury was caused to another person.

The Law

All references in this section to statutory sections refer to the Road Traffic Act 1988 unless otherwise indicated. The section will concentrate on the following offences: 

  • driving (or in charge) when under the influence of drink or drugs (section 4); 
  • driving (or in charge/attempting to drive) with excess alcohol (section 5); 
  • failing to provide a specimen of breath for screening (section 6(4)); 
  • failing to provided a specimen for analysis (section 7(6)).

When a death has occurred as a result of dangerous or careless driving when under the influence of drink or drugs you should refer to (Road Traffic Offences - Prosecuting Cases of Bad Driving, elsewhere in the legal guidance)

Charging Practice/Acceptability of Pleas

In most cases of drink/driving, there will be scientific and/or medical evidence to show that the driver has exceeded the prescribed limit. In such cases a charge under section 5 will be proper.

Although the prescribed breath alcohol limit is 35 micrograms, a driver will not be prosecuted under section 5 with a breath alcohol level of less than 40 micrograms. This is in accordance with the guidelines contained in Home Office circular 46/1983. That level will usually be taken as that recorded by an evidential breath testing machine or by analysis of a blood/urine sample. However, it may be the level as determined by back calculations.

Impairment/Unfitness to drive

If there is clear evidence of impairment over and above the evidence of the breath analysis you should consider charging a section 4 offence in preference to that under section 5.

Provided that the evidence supports an allegation of unfitness, joint proceedings for both section 4 and 5 offences are normally unnecessary. But you should consider charging both when: 

  • the evidence indicates impairment as a result of both drugs and excess consumption of alcohol; 
  • there is a possible defence to the section 5 offence on the grounds that the sample taken by the police is likely to be ruled inadmissible.

Where there is evidence to support unfitness for a charge under section 4, and also evidence to support an allegation of failing to provide a specimen for a laboratory test under section 7(6), you may charge both offences. That may be particularly appropriate if there is a possible defence to the charge of failing to provide a specimen.

Failing to provide a specimen

A charge of failing to provide a specimen of breath for screening under section 6(4) should be preferred when supported by the evidence. In the event of a guilty plea being tendered to a related offence under sections 4, 5 or 7(6) it will not normally be in the public interest to proceed with the charge under section 6(4).

There is no need to state in a charge under section 7(6) the offence which is suspected and being investigated by a police officer: see DPP v Butterworth (1994) 3 WLR 538. It is the fact that an investigation is in process which gives rise to the requirement to provide a specimen for analysis. The nature of the offence under investigation is relevant only to penalty; it may be necessary to have a "Newton" hearing to determine if the defendant had driven, or was in charge of, a vehicle on a road.

Admissibility of the National Drink Pro Forma - Form MG.DD

In the event of a not guilty plea to a summary drink/drive offence you should try to obtain a formal admission under Section 10 of the Criminal Justice Act 1967 as to the contents of the Form. Such an admission must include the name of the defendant, the date and place of the offence and the results of the breath test or of the laboratory test. If such an admission cannot be secured then the officers conducting or witnessing the sampling procedure will normally have to be called to give evidence in person.

The Form MG DD contains assertions of fact, it is a document made out of court and is inadmissible under the hearsay rule. Section 9 of the Criminal Justice Act 1967 only permits that the evidence contained in a witness statement is admissible were the maker of it in the witness box. If the officer who filled out the Form were in the witness box he could not produce the Form in chief as an exhibit, though he could refer to it as a memory refreshing document. The production in evidence of that Form attached to a short Section 9 CJA statement will not render the content admissible.

The only way in which the information contained on a Form MG DD can be produced in documentary form as admissible evidence is if that information is extracted from the form and incorporated into a Section 9 CJA statement made by the officer. This course must be followed in the event of a prosecution under section 3A of causing death by dangerous driving when under the influence of drink or drugs.

Disclosure of Unused Material

Standard records, such as the maintenance log for each instrument, does not form part of the investigation into an offence, will not form part of the standard part of the unused material of an investigation, and should not be routinely disclosed to the defence.

The defence may request copies of technical documents relating to the specification, construction and performance of the instruments. Disclosure to the defence of such unused material is governed by the usual CPIA rules on defence material, and see also DPP -v- McKeown, DPP -v- Jones (1997) RTR 162. You should bear in mind that material in this category may be commercially confidential. In cases of difficulty advice should be sought from the Policy Directorate at HQ.

If there is any reason to believe that an instrument whose readings are relied upon in evidence was not working correctly that information, which will undermine the prosecution case, must be disclosed to the defence.

The Role of the Manufacturers

It may be necessary in cases of difficulty to contact the manufacturers. Contact should initially be made through the police.

Further reading