Cocaine Drug Driving Offences

The legal limit for Cocaine is 10 micrograms per litre of blood (10ug). This is a zero tolerance limit. If convicted, you would receive a 12 month driving disqualification. 

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  • Finding fault with police procedure
  • Challenging blood results 
  • Identifying defences
  • Next steps 

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Drug Driving & Cocaine


Illegal Drug

Legal Limit

Cocaine 10µg%

Cocaine is a powerful and highly addictive controlled substance. The legal limit for cocaine is 10 micrograms per litre of blood (10ug/L). This is a 'zero tolerance' legal limit, meaning even a small amount of cocaine can put you over the limit. There is no requirement for the CPS to prove that you were impaired. 

Will cocaine affect your driving?

Cocaine use may not adversely affect your driving. The effects of cocaine on driving will depend on;

  • how much cocaine is taken,
  • your tolerance to the drug, and
  • the use of any other drugs, including alcohol.

The stimulant effects of cocaine last for only a short period of time following which the after-effects commence. It has been reported that one-off use of cocaine by people who are tired can actually improve attention for a short period of time with subsequent improvement in performance of simple tasks. 


The after-effects of cocaine use include;

  • Poor concentration and coordination
  • Drowsiness
  • Lapses of attention and ignoring stimuli such as traffic light changes
  • Visual impairment, primarily caused by an increased sensitivity to light

A study of motorists driving under the influence of cocaine found that, although they displayed symptoms of cocaine use, nearly half performed normally on field sobriety tests.

How long does cocaine stay in your system?

Cocaine will remain in your system for up to three days following use – and even longer in frequent users. Cocaine levels peak in the blood an average of 30 minutes after ingestion.

One way to measure cocaine levels is the ‘half-life’. This is the period of time required for the amount of drug in your system to be reduced by one-half. Different drugs have different half-lives. 

The half-life of cocaine is one hour. This means that if you took a 'line' of cocaine at 8:00pm, by 9:00pm there would be 25mg remaining in your system. By 10pm, there would be 12.5mg in your system, and so on… The quantity of the drug will reduce by 50% over each ‘half-life’ period.

So, how much cocaine before you’re over the limit?

Cocaine appears in blood after about 20 minutes, reaching a maximum concentration in 30 to 50 minutes.

Intranasal administration (through your nose) of a 32mg dose of cocaine (an average ‘line’) would produce a blood concentration of between 40-80 micrograms within 40 minutes (the legal limit being 10 micrograms). Your body would eliminate 50% of this within one hour.

If, for example, you consumed a 32mg line of cocaine at 8:00pm, your blood concentration will peak at 60 micrograms in 40 minutes. Within one hour, your body will have eliminated half the amount, meaning your blood content at 9:00pm would be 30 micrograms. By 10:00pm, it would be 15 micrograms. By 11:00pm you’d be under the limit for cocaine.


Even if you're under the legal limit for cocaine, you could still be over the benzoylecgonine. This is the breakdown metabolite of cocaine, and will remain in your system for days (sometimes weeks) following consumption. You can read more about benzoylecgonine on our webpage.

Drug Driving Cocaine Defences

How we win cocaine cases

Cocaine is a difficult drug to analyse. This presents practical problems for laboratories when trying to provide accurate results. Every cocaine case is different and could be challenged in a different way. If you'd like one-to-one advice about your case, please get in touch today. 

  • The 20% Rule - Has it been applied? 

    The police use a complex and technical method of analysis referred to a LC-MS. This method is considered the 'gold standard' in commercial large-scale drug testing. The trouble is, mistakes are still being made. It doesn't matter how accurate the testing process is if the staff aren't trained or qualified. Human error cannot be avoided. To get around this problem, the laboratory has to deduct a percentage figure from the final test result. The lab refers to this a 'normal analytical variation' which, in reality, means 'if we get it wrong'. In cocaine cases, they're required to knock-off 20% from the final result. 

    By law you are allowed to check the accuracy of the analytical process. The CPS must supply the Analytical Data Pack containing all the technical data relating to the testing of your sample. You can then check whether the sample was analysed correctly, and whether the 20% has been deducted. 

    Disclosure Issues

    As above, you are allowed to access the technical data relating to your sample. Under Part 19 of the Criminal Procedure Rules, this technical data should be made available to you 'as soon as practicable' following a not guilty plea. But what happens if it's not disclosed? M.A.J Law would estimate that in over 80% of drug driving cases the CPS will fail to disclosure the correct evidence in time. We can then apply under the same section of the CPR to exclude the evidence against you. Due to the number of drug driving cases combined with technical issues, the CPS continue to disclose evidence late.

The information from this page come from a study conducted by Edward J. Cone. The information above it based on averages and will vary from person to person. It should not be used as a calculation method to avoid driving whilst over the prescribed limit. Cocaine is a prohibited substance.