Drug driving with cannabis over the legal limit

Drug Legal Limit
Delta-9-Tetrahydrocannabinol 2ug/L

Cannabis ( Delta-9-Tetrahydrocannabinol THC )*1

Cannabis is the common name for the plant Cannabis Sativa which contains a large number of active compounds known collectively as cannabinoids, the most important of which is tetrahydrocannabinol.

It acts as a mild sedative and is often used to reduce anxiety. It is the most commonly used illicit drug in the UK.

DRUG DRIVER
How cannabis works in your body

If smoked THC is absorbed rapidly in the lungs and the concentration peaks quicky, within a few minutes. The peak effects occur about 15 – 30 minutes later and last about 2- 4 hours.

If ingested (eaten) the onset of the effects are slower but can last longer for up to 8 hours.

It is very fat soluble and is rapidly deposited in fatty tissue around the body. As a result THC may leak out into the bloodstream over a longer period of time after the last use.

Cannabis can contain different levels of THC so it is impossible to calculate what the level may have been in the cannabis consumed unless tested in a laboratory. Home grown cannabis may contain THC in excess of 30% whilst foreign imports are much lower at 3-4%.

The 9th Report of the House of Lords Science and Technology Committee 1998 defined the categories of cannabis users:

A casual user – someone who is an irregular user, smoking in amounts of up to 1g at a time but not more than 28g per year.

A regular user – someone smoking 0.5g per day in three to four joints. There is about 150mg per spliff - adding up to about 3.5g per week.

A heavy user – is someone smoking more than 3.5g per day/28g per week. Someone in this category is likely to be permanently “stoned”.

Generally if you smoke a typical joint you will peak at about 120ug after a few minutes so you should never drive immediately after smoking cannabis. However this will rapidly fall over the next 4- 6 hours and depending on your average usage, for a casual user you would be below the limit of 2ug within 8 – 12 hours. If you are a heavy user you are likely to be over the limit most of the time.


Medical Cannabis

From 1 November 2028 patients can be prescribed medicinal cannabis by specialist doctors.

It is considered highly beneficial to patients suffering from serious mental health issues and neurological conditions such as MS. The patient must have an unmet clinical need that cannot be met by licensed products.

Such a prescription will provide such drivers with a legal defence.

This presents issues with the carer’s of such patients who are often exposed to significant levels of THC.

We successfully represented such a carer who was found to have 7ug of THC in his blood and managed to get the case discontinued on the basis it was not in the public interest to prosecute a carer of a patient who had prescribed cannabis.


Cannabis and Driving

Several studies have shown that THC impairs driving. The maximum impairment is usually about 30 -45 minutes after smoking but will reduce gradually over the following 2 – 3 hours.

Interestingly some surveys show that cannabis user tend to adjust their driving accordingly so whilst impaired they are probably not as high as risk as someone who has taken “cocaine”.

Impact of cannabis effects on your driving

  • Slower Reactions time – therefore a greater distance is travelled before reacting increasing the risk of collisions.
  • Lack of Coordination - reduce your ability to manage the vehicle when driving and react appropriately to any emergency
  • Reduced Concentration – increases the risk of missing road signs, failing to indicate or see dangers in the road.
  • Decreased Vision – increasing the risk of missing road signs, pedestrians, other road users and failing to see dangers in the road
  • Inhibits judgement – so you are more likely to drive whilst impaired do to cannabis and also hinders you ability to assess a dangerous situation to react in a safe and effective manner


The legal limit for THC

The Govt introduced specific legal limits for both illicit and prescribed drugs in March 2015 when the offence of driving above the specified limit for drugs was introduced.

The specified limit for THC is 2ug. This is a measurement that is 10,000 fold lower than the analysis for alcohol and the analysis is not subject to the type approval or a presumption that the result is correct. This leads to greater uncertainty in results.

The government did not accept the recommended levels which were set in the Wolff report. The report recommended that the level for THC should be 5ug at which they determined a driver would be impaired.*2


Defences for driving over the legal limit for cannabis

Laboratories have struggled to effectively analyse blood samples. There have been two laboratories recently which have lost their accreditation due to errors in their analysis of blood samples for cannabis. Approximately 4,000 cases have been re-opened and convictions set aside as a result. It is not a perfect science and you cannot assume that the prosecution analysis is 100% accurate it isn’t.


What to look for?

There a number of tell tale signs in the analytical data pack (ADP) which would indicate the result are unreliable.

  • Has the laboratory deducted the 30% allowance from the result – this is the allowed margin of error. If not then your result may be below the specified level.
  • Does the laboratory have the proper accreditation which is the validation process which examines their processes to ensure their accuracy in analysing blood samples. There is an accepted 30% allowance between laboratories. Such an allowance suggests that if another laboratory tested the same sample it could come back 30% lower and that is difficult to challenge.
  • Poor labelling and lack of continuity. All vials must be labelled correctly and followed through the analysis sometimes this gets muddled up and the prosecution cannot prove that the sample tested was the defendants.
  • Has the data in put been accurate if there is a “data anomaly” it will usually lead to inaccurate results.
  • Failings in the quality control sample – each batch of samples must have a control sample to be measured against if this is contaminated in any way the whole batch would usually need to be re-tested but usually isn’t. Such contamination would lead to higher results and render the results unreliable.
  • Have they calibrated the results and equipment accurately. The laboratories must test and calibrate their analytical instruments daily. These results must fall within a recommendation range or standard deviation. These are resulted in the form of graphs on the ADP which can be examined and the deviation checked to see if they fall within the recommended range if not the batch should have been re-tested because the results will not be reliable. Laboratories seldom re-test because it is not profitable to do so their margins for profit are so small.


Post Driving Consumption

Many drivers say that when the police are indicating them to stop driving, they panic because they are in possession of some cannabis so having stopped their vehicle and before the police reach them they eat the cannabis.

This is a defence but we would have to prove this on a balance of probabilities. We would have to show that but for the cannabis eaten you would have been under the limit. If done successfully you would be found not guilty and your case would be dismissed.

The police may have body worn video evidence which will either show that you may have taken cannabis or had the time to take cannabis. Equally it may also show that it was impossible for you to take the cannabis.

You will usually need expert evidence to show that but for the cannabis taken after driving you would not have been over the limit.

If you have eaten drugs after being stopped then you should tell the police. It makes the argument of post driving consumption more believable.


Procedural Issues

The prosecution must follows the procedure to the letter, there include:

  1. Compliance with S15 Road Traffic Offenders Act 1988 which specifies how blood samples should be taken and what should be done with them after.
    https://roadtrafficdefencelawyers.co.uk/2023/03/14/the-importance-of-keeping-your-blood-sample-taken-by-the-police/
  2. Lack of continuity of the sample. The police must be able to show that the sample tested was your sample and failure to label correctly can break the continuity and offer a defence.
  3. Failure to disclose evidence which will assist the us as the defence or undermine the prosecution case. The prosecution often fail to serve evidence within a specified period of time and this can lead to arguments to exclude vital prosecution evidence such as the expert report.


Special reasons and cannabis

Special reasons can be argued where you have unwittingly taken cannabis in order to avoid the mandatory minimum 12 months ban.

  • Cannabis oil – some cannabis oil still contains THC and if this is not labelled then you may be able to plead special reasons to avoid a disqualification
  • Brownies – some people will make brownies/cookies with cannabis in them and it is difficult to know. If you have consumed these not knowing that they contain cannabis you may be able to plead special reasons.
  • Passive smoking – the legal limit of 2ug has been set to avoid passive smokers being over the legal limit but this is not particularly accurate. It is not a defence and can only be argued to avoid the disqualification. However, if you use cannabis at all it will be more difficult to successfully argue special reasons. Also if you are aware you are in a room full of cannabis smokers so would be aware of the risk. You would need to witnesses to support your contention you were not a user but were in an environment where cannabis was being smoked. We would also obtain an expert report to show that this would account for the level of THC in your system. If it all adds up you would have a successful special reasons argument.


Reference

  1. Symptoms and Signs of Substance Misuse 3rd edition Margaret Stark, Jason Payne-Jamesm Michael Scott-Ham
  2. Wolff Report 2013