How Do Police Test for Drug Driving?

Drug driving cases generally have to be prosecuted within six months of the date the offence was allegedly committed. This can mean that people who have been caught are left in a state of uncertainty because a charge might be brought weeks or even months after the initial incident, especially if there are administrative delays or problems in processing test results. For more serious cases or when further investigation is required, the time limit for bringing charges may be extended. As such, you may feel a false sense of security only to be hit unexpectedly with a court summons.

It is also possible that other related charges, such as dangerous driving or causing death by dangerous driving, could be brought against the person alongside a drug driving charge, and these offences may have different time limitations. If you have been subjected to a roadside drug test and are concerned about what the results might mean, contact a legal professional from JMW’s drug driving defence team. We can let you know what to expect next and how to formulate the best response.

Blood tests conducted by the police for the purpose of determining drug or alcohol levels in the UK are generally considered to be highly accurate. These tests are conducted under controlled conditions, in a laboratory, and are subject to rigorous protocols to ensure their accuracy and reliability. These tests detect a variety of substances but are primarily focused on any legal or illegal drugs in your system that might impair your ability to drive safely.

Drug driving tests are generally only administered after a roadside test has indicated the presence of drugs or alcohol. If the blood test confirms the presence of drugs or alcohol above the legal limits, this is strong evidence in a court of law. A substance does not have to be a specified controlled drug to result in a conviction - some prescription medicines can also affect your ability to drive.

Samples are usually divided into two vials: one for initial testing and another to be used by the defence for independent testing, should they choose to contest the results. However, test results and evidence-collection procedures are not 100% foolproof, and there may be scope to challenge them.

There can be issues related to the handling, storage, and testing of blood samples, or even human error. Chain-of-custody protocols must be rigorously followed to maintain the integrity of the samples, and if police fail in this, it could form part of your defence. In rare cases, there may be medical or other factors that could potentially affect the accuracy of the test, and you may be able to mount a medical defence.

If you are facing charges based on blood test results, you should consult with a driving offence solicitor at JMW for advice on the possible outcomes and the steps you can take to mount a defence.

If police suspect you of exceeding drug driving limits, they may administer a roadside drug test. This typically takes the form of the field impairment assessment described above, and a police officer will take you through these procedures to evaluate your capacity to drive. If the tests suggest you are unfit to drive, either because it returns a positive result or because there are other grounds for suspicion, you will be arrested and taken to a police station for further tests.

You must give informed consent for a blood test. You can refuse, but doing so comes with the risk of very serious penalties, including a custodial sentence and the suspension of your driving licence.

If you agree to give the sample, a healthcare professional, usually a nurse or a doctor, will draw the blood. In most cases, blood is drawn into two separate vials: one for analysis by the prosecution and the other reserved for independent testing by the defence if required. The vials are securely sealed and labelled to establish a chain of custody.

The samples will be sent off for analysis, after which the police will receive a report containing your drug-driving blood test results. How long it takes to receive the results will depend, and this could introduce delays before the police decide whether or not to charge you.

UK police generally need a "reasonable suspicion" to stop and test a driver for drug use. This could be based on the manner of the person's driving, the condition of the vehicle, or information they have received that indicates the driver may be under the influence of drugs. Once the vehicle is stopped, signs such as the driver's behaviour, speech, or physical indicators could further support reasonable suspicion and justify a roadside drug test.

Refusal to submit to a drug test when requested can lead to arrest and may result in charges, which could ultimately lead to a driving ban, fine, or imprisonment if convicted. However, if you believe that the police did not have a good reason to test you for drugs, this might be used in your defence.

The UK's drug driving laws also cover prescription medications if they impair driving ability. You can be prosecuted for driving above drug driving limits, whether the substances are legal or illegal drugs. This means that anything from cannabis and cocaine to prescribed amphetamine and opium-based drugs, provided operate a motor vehicle after exceeding specified limits.

When you take some medicinal drugs, you may be advised not to operate heavy machinery. You do not need to exceed a prescribed limit that your doctor has offered for these substances in order to be convicted of a drug driving offence - only the legal limit, which may be much lower than your dose. Seek advice from a medical professional about your fitness to drive when taking your medication if you have any concerns about facing legal consequences.