7 Things That Happen When You Fail a Roadside Drug Test in the UK

Published by Drug Driving Solicitors, specialist defence lawyers for drug driving charges across England and Wales.

Being stopped by the police and asked to take a roadside drug test is a stressful experience, and it becomes considerably more stressful if that test comes back positive. Many drivers going through this process for the first time have no idea what happens next, how long it might take, or what their rights are at each stage. Understanding the sequence of events can make a genuinely difficult situation feel a little more manageable.

This article walks through what typically happens after a positive roadside drug swab, from the moment the device gives its reading through to a potential hearing at the Magistrates' Court. Every case is different, and the exact path yours takes will depend on the circumstances, but the following seven stages cover the process that most drivers will encounter.

The Roadside Device Produces A Positive Reading

The roadside drug testing device used by UK police forces, commonly known as a drugalyser, screens for the presence of cannabis and cocaine. It works by taking a saliva swab, which is then analysed within a couple of minutes. If the device indicates a positive result for either substance, the officer has grounds to take further action.

It is worth understanding that this initial device is a screening tool rather than a precise measurement instrument. It tells the officer that a substance is likely present above a certain threshold, but it does not measure the exact concentration in your body. That more detailed analysis comes later in the process, at the laboratory stage.

A positive roadside reading on its own is not a conviction, and it does not automatically mean you will be prosecuted. It is simply the trigger that allows the officer to proceed to the next stages of the procedure, which are designed to confirm or dispute the initial finding through more rigorous testing.

Drivers are sometimes surprised that certain other drugs, such as ketamine or MDMA, are not detected by the roadside device at all. If an officer suspects impairment from a substance the swab does not test for, they may rely on a Field Impairment Test instead, which involves a series of coordination and observation checks rather than a chemical reading.

The Officer Administers A Statutory Warning

Before requiring you to provide a specimen, the officer is legally required to give you a statutory warning. This is a formal explanation that failing to provide a specimen, without reasonable excuse, is itself a criminal offence. It is a procedural safeguard intended to make sure drivers understand the seriousness of what is being asked of them.

The warning does not need to be delivered in any particular set of words, but its substance must be communicated clearly. Officers are trained to deliver it as part of their standard roadside procedure, and it is usually given immediately before or after the roadside swab is requested, depending on the force's practice.

This step matters more than many drivers realise. If the warning was not given correctly, or was not given at all, it can form part of a legal challenge later on. Solicitors experienced in drug driving cases routinely check the bodycam footage and custody record to confirm this step was properly followed.

For most drivers, this stage passes quickly and without incident, simply forming part of the natural rhythm of the roadside stop. It is nonetheless one of the procedural checkpoints that a specialist solicitor will always review when assessing whether a case has been handled correctly from start to finish.

You Are Arrested And Taken To A Custody Suite

Once the roadside device shows a positive result, the officer will generally arrest the driver on suspicion of driving while unfit through drugs, or of driving with a specified controlled drug above the legal limit. This might feel alarming, but an arrest at this stage is a standard part of the procedure rather than a sign that the outcome is already decided.

At the police station, you will be booked into custody in the usual way. Your details will be recorded, you will be informed of your rights, and you will be given the opportunity to have a solicitor present. It is generally a good idea to take up this offer, even if you feel the situation is straightforward, since a solicitor can make sure the correct procedures are followed from this point onward.

The custody suite is also where the next evidential step takes place. Officers will explain that a blood sample is required to confirm the roadside result with greater accuracy, and they will arrange for a suitably qualified person to take it. This is a legally distinct step from the initial swab, with its own set of procedural rules that must be observed.

Most drivers spend a limited period of time in custody before being released, usually on bail while further enquiries are made. It is common to feel disoriented during this stage, so it can help to remember that release on bail is a normal part of the process and not an indication of guilt.

A Healthcare Professional Takes A Blood Sample

Because the roadside device is a screening tool, the law requires a more precise method of confirming the presence and concentration of a controlled drug. This is done through a blood sample, which must be taken by a healthcare professional such as a nurse or doctor, rather than by a police officer.

The healthcare professional will explain the procedure and take two samples from the same draw. This is an important safeguard: one sample is sent for laboratory analysis, while the other is retained and offered to the driver, giving them the option to arrange an independent analysis of their own if they wish to challenge the result.

There are strict rules around how the sample must be taken, stored, and labelled, often referred to as the chain of custody. Any break in this chain, such as incorrect labelling or an unexplained gap in the paperwork, can become a significant point of legal argument later in the case.

Once both samples have been taken and properly documented, you will usually be released from custody while the retained sample is sent away for detailed testing. This is often the point at which the practical, day-to-day impact on your life becomes less immediate, even though the legal process is still very much ongoing.

The Blood Sample Is Sent For Laboratory Analysis

The sample sent by the police goes to a forensic laboratory, where it is tested using precise analytical methods capable of measuring the exact concentration of a controlled drug in the blood. This is compared against the specified legal limits set out in the Road Traffic Act 1988 for each listed drug.

This stage often takes the longest amount of time in the entire process. Laboratories work through a queue of samples from across the country, and turnaround times can vary considerably depending on the force involved and current demand. It is common for drivers to wait several weeks, or even a few months, before a result is confirmed.

The laboratory report is a central piece of evidence in any subsequent prosecution, and it is also one of the areas most closely scrutinised by defence solicitors. Analytical errors, contamination issues, and documentation gaps do occur, and a specialist lawyer will know exactly what to look for when reviewing the report on a client's behalf.

While waiting for results, it is entirely natural to feel uncertain about what comes next. Keeping in touch with a solicitor during this period, even just for periodic updates, can help make the waiting period feel less like a void and more like a managed process.

You Are Charged Or Told No Further Action Will Be Taken

Once the laboratory result is available, the police and the Crown Prosecution Service will decide how to proceed. If the concentration was below the specified limit, or if there are other evidential problems with the case, you may be told that no further action will be taken. This closes the matter and removes any live legal proceedings against you.

If the concentration is confirmed above the specified limit, and no valid statutory defence applies, you will usually be charged by post or asked to attend a voluntary interview beforehand. This notification will set out the offence you are alleged to have committed and give a date for your first court appearance.

This is a natural moment to seek specialist legal advice, if you have not already done so. A solicitor experienced in drug driving law can review the entire case file at this stage, including the initial device readings, the statutory warning, the blood sample procedure, and the laboratory report, to identify any grounds for challenging the charge.

Being charged is understandably an anxious experience, but it is important to remember that a charge is simply the start of the court process, not its conclusion. Many cases are successfully defended, or result in reduced penalties, once all the evidence has been properly examined.

Your Case Is Heard At The Magistrates' Court

Drug driving cases are dealt with in the Magistrates' Court, and your first hearing will usually be a short administrative appearance to confirm your details and enter a plea. Depending on how the case is being conducted, this and the following hearings can sometimes be handled without you needing to attend in person, though this depends on the specifics of your case.

If you plead not guilty, a trial date will be set, and the prosecution will need to prove its case using the evidence gathered throughout the earlier stages, from the roadside device to the laboratory report. Your solicitor will have the opportunity to challenge any part of that evidence that appears flawed or improperly obtained.

If you plead guilty, or are found guilty after a trial, the court will move to sentencing. This typically involves a mandatory minimum 12-month driving disqualification, along with a fine and possibly other penalties, the exact combination depending on the circumstances of the offence and any mitigating factors presented on your behalf.

Throughout this stage, good legal representation makes a genuine difference, both in terms of how the case is argued and how any mitigation is presented to the court. A solicitor familiar with drug driving law will understand which arguments carry weight with magistrates and how best to present your personal circumstances.

Understanding Where You Stand

Failing a roadside drug test sets in motion a defined legal process with several distinct stages, each of which carries its own procedural requirements and its own opportunities for a case to be properly reviewed or challenged. Knowing what to expect at each step, from the initial device reading through to a potential court hearing, can make the experience considerably less daunting and helps you make informed decisions about seeking legal advice early.

Frequently Asked Questions

What if the drug found in my blood was prescribed by my doctor?

There is a statutory medical defence under Section 5A(3) of the Road Traffic Act 1988 available to drivers who can demonstrate that the drug was lawfully prescribed or supplied to them, that they took it in line with medical guidance, and that it did not impair their driving. This defence exists, but it is more limited than many people assume and needs to be carefully evidenced and argued. Drug Driving Solicitors has particular experience handling cases involving prescription medication.

Do I need a solicitor if I am planning to plead guilty?

Yes, it is still worth seeking advice even if you intend to accept the charge. A solicitor can check that the evidence was gathered lawfully, ensure any statutory defence has not been overlooked, and prepare mitigation that may influence sentencing, such as the length of any disqualification or the size of any fine. Pleading guilty without advice can mean missing an opportunity to improve the outcome.

Can I continue driving while I wait for the laboratory results?

Unless you have already been charged with bail conditions restricting your driving, or you are disqualified for a separate reason, an ongoing investigation does not by itself prevent you from driving. That said, it is worth checking your insurance policy, as some require disclosure of a pending criminal investigation. When in doubt, it is best to ask your solicitor.

What are the most common reasons a drug driving charge gets dropped?

The most frequent grounds include an incorrectly delivered statutory warning before the roadside swab, use of equipment not approved for the drug being tested, issues with how the blood sample was handled or documented, failure to offer the driver their retained sample, laboratory errors, and unlawful stop and search procedures. A specialist solicitor examines all of these areas, not only the final test result.

What does a DG10 code mean and how long does it remain on my licence?

DG10 is the DVLA code used to record a conviction for driving, or attempting to drive, with a controlled drug above the specified limit. It stays on your licence for 11 years from the date of conviction and is visible to insurers checking the DVLA record, often leading to a noticeable rise in premiums. A specialist solicitor can talk you through what a DG10 conviction might mean for your particular circumstances, including work and travel implications.

What should I do if I refuse to give a blood sample at the police station?

Refusing to provide a specimen without a reasonable excuse is a criminal offence in its own right under Section 7A of the Road Traffic Act 1988, carrying penalties equivalent to a drug driving conviction, including the mandatory 12-month disqualification. Reasonable excuses are defined narrowly, and any medical reason needs to be properly evidenced. Speak to a solicitor before refusing a sample.

How long does it usually take from a failed roadside test to being charged?

The process generally takes somewhere between 2 and 6 months, sometimes longer. The main source of delay is laboratory analysis of the blood sample, which depends on the relevant force's laboratory and its workload at the time. A charging decision is normally reached fairly promptly once the laboratory report comes back. If more than 6 months have passed without any update, it is worth getting specialist legal advice on where things stand.

Drug Driving Solicitors is a specialist firm dealing with drug driving cases throughout England and Wales. If you have failed a roadside drug test and would like to understand where you stand, get in touch for a free initial consultation or visit drugdrivingsolicitors.co.uk. Advice at this early stage costs nothing, and it can make a real difference to how your case turns out.