What happens if you fail a UK roadside drug test? Step-by-step process
Failed a UK roadside drug test? The officer will arrest you on suspicion of drug driving under Section 5A of the Road Traffic Act 1988, take you to the nearest police custody suite, and ask a healthcare professional to take a blood sample for laboratory analysis. The roadside swab is a screening test only — the prosecution case is built on the station blood reading, which usually takes six to twelve weeks to come back. From the swab to a court outcome, the process runs through seven distinct stages, each with rights and decisions that affect how the case ends.
Start Today
Enter your details below for a free initial call.
This guide walks through every stage from the roadside positive to sentencing. For the underlying science on how long drugs show on a swab, see the complete guide to cocaine and UK roadside drug testing. For specialist defence work after charge, book your free confidential consultation.
Step 1 — The roadside positive result and your immediate arrest
The roadside swab is the DrugWipe 5S device, a hand-held cartridge that screens saliva for cocaine, cannabis, opiates, amphetamines and benzodiazepines. A positive band appears within three to eight minutes of the sample being taken. The officer reads the result on the spot.
A positive swab does not, on its own, prove that you are over the legal limit. It is a screening tool with a sensitivity threshold lower than the prosecution threshold, and its specificity has been documented at below 100% in independent testing. That is why the device cannot convict you — it can only provide the reasonable suspicion an officer needs to arrest. The science of challenging the swab result belongs to a later stage; for now, the practical reality is that a positive reading means you are going to be arrested.
The officer will caution you, place you under arrest under Section 5A of the Road Traffic Act 1988, and either handcuff you or ask you to come voluntarily. Your vehicle will normally be recovered to a police-approved pound at your cost, or in some cases left at the scene if a sober second driver is available to take it home.
The single most useful thing you can do at this stage is to stay silent beyond confirming your name, address and date of birth. Anything you say roadside about drug use, the previous evening, or your driving will end up in the officer’s pocket notebook and may be put to you in interview at the station. You have a right to silence and a right to legal advice. Use both.
Step 2 — Transport to the police custody suite
You will be transported to the nearest custody suite that is open and staffed. In rural areas this can mean an hour or more in the back of a marked car. On arrival the custody sergeant will book you in, log your property, take fingerprints, a DNA sample and a photograph, and ask whether you want to speak to the duty solicitor. The answer is always yes, even if you intend to instruct a private solicitor later.
The custody clock starts ticking from the moment you arrive. The police have an initial 24 hours to deal with the case before they must either charge you, release you, or apply to a superintendent for an extension. For a straightforward drug driving case, most of that 24-hour window is spent waiting for the healthcare professional to attend and take the blood sample.
You will be placed in a cell during the wait. You are entitled to food, water, a blanket, access to a toilet, and a phone call to one person to let them know where you are. If you have a medical condition, prescription medication, or any disability that affects your detention, tell the custody sergeant at booking-in — it is recorded on the custody record and can become important later if the procedure is challenged.
Step 3 — The station blood (or urine) specimen
The healthcare professional — usually a forensic medical examiner or a registered nurse — will explain the procedure and ask you to consent to a blood sample under Section 7 of the Road Traffic Act 1988. Refusal at this stage is itself a separate offence. We cover [refusing the roadside test as a separate offence](https://scarsdalesolicitors.com/refusing-roadside-drug-test-uk/) in its own guide; station refusal works the same way and carries the same penalties as the drug driving offence itself.
In a small number of cases, blood cannot be taken — usually for a documented medical reason such as a needle phobia, certain blood disorders, or active anti-coagulant treatment. If you have one of these conditions, say so before the procedure begins, ideally with a GP letter or prescription as evidence. The healthcare professional will then decide whether to take urine instead. Urine analysis is technically valid but produces a wider margin of error and is more straightforward to challenge.
The sample itself is small (typically 10ml drawn into two sealed vials). It is logged in the custody record, sealed in the presence of an officer and the healthcare professional, and despatched to an accredited forensic laboratory — usually Eurofins or SYNLAB Laboratory Services UK. Turnaround is currently running at six to twelve weeks. During that window you will normally be released on bail or under investigation; the analysis is what determines whether you are charged.
For substance-specific detail on the analytical thresholds, see the guides on the station blood test for cocaine, the cannabis drug driving offence for THC readings, and prescription medication drug driving for legitimately prescribed medicines that can produce a positive reading.
Step 4 — The optional second sample (why you should always take it)
Under Section 15 of the Road Traffic Offenders Act 1988, you have the right to ask for a second sealed sample of the blood specimen to be retained, so that you (or your solicitor) can have it independently analysed if the prosecution reading is challenged.
The healthcare professional must offer this. If you are not offered it, that is a procedural failure that can be relied on at trial — but the better outcome is to take the sample. It is the only piece of evidence in the case that you control. If the prosecution reading is close to the legal limit, an independent re-analysis can move a borderline case across the line into reasonable doubt.
The cost of independent analysis runs to roughly £400 to £700 depending on the substance and the laboratory. You do not have to commit to the analysis at the time of the sample; you just have to take possession of the sealed second vial. Most defence solicitors only commission the re-test when the prosecution reading suggests it is worth doing. But you cannot commission what you do not hold, so the rule is simple: always accept the second sample.
Step 5 — Charge, bail or release without further action
When the blood analysis comes back, the police have three options. They can charge you and bail you to a first appearance at the Magistrates’ Court (the most common outcome where the reading is meaningfully above the limit). They can charge you and require you to attend court on a specific date without bail conditions. Or they can release you with no further action if the reading is below the legal limit, the chain of custody is broken, or the Crown Prosecution Service legal guidance indicates the case is not in the public interest to prosecute.
Bail conditions for drug driving are typically light — a residential condition (you must live at the address given) and sometimes a not-to-drive condition pending the case. The not-to-drive condition is administrative, not a disqualification, but breaching it is a separate offence in itself.
If you were released under investigation rather than bailed (a common interim position while the analysis is processed), you will receive a postal requisition by recorded delivery containing the charge and the first court date. The letter usually arrives between eight and sixteen weeks from the date of arrest. Open it the day it arrives — the first hearing date can be as little as fourteen days away, and the time to instruct a solicitor is now.
Step 6 — Your first court appearance and the plea decision
The first hearing is at a Magistrates’ Court, almost always the one local to the place of arrest rather than your home address. The hearing itself is short, often under twenty minutes, and the substantive issue is your plea.
A guilty plea at the earliest opportunity attracts the maximum one-third sentencing discount under the Sentencing Council’s guidelines. A not guilty plea sets a trial date, normally four to eight weeks out, and the case proceeds to disclosure of the prosecution evidence (analytical report, custody record, officer statements). This is the decision point where having taken legal advice in advance — rather than reacting on the morning — changes outcomes.
You are entitled to a duty solicitor at the first hearing if you have not instructed your own. The duty solicitor will read the papers in the cells and give you a view on plea, but they will only have minutes to do so. A privately instructed solicitor will have spent days on the evidence before the hearing and will be in a position to tell you whether the reading is challengeable, whether the procedure was clean, and whether the section 5A(3) statutory defence applies in your circumstances. If you intend to fight the case, the decision to instruct should be made before the first hearing, not at it.
For the full menu of defences and how they are deployed in court, see the drug driving solicitors national hub.
Step 7 — Trial or sentencing
If you plead guilty, the magistrates will move to sentence either immediately or at a short adjournment for a pre-sentence report. Drug driving carries a mandatory minimum 12-month disqualification, an unlimited fine assessed against weekly income (Band C in the Sentencing Council’s drug driving guideline), and a discretionary custodial sentence of up to six months in aggravated cases. The drug driving sentencing structure sets out where in the band any particular reading is likely to fall.
If you plead not guilty, the case goes to trial in the same Magistrates’ Court (drug driving is summary-only and cannot be sent to the Crown Court). The trial usually lasts a single day. The prosecution call the arresting officer, the healthcare professional and, in contested analytical cases, the forensic toxicologist. The defence case is whatever has been built between charge and trial: independent analysis of the second sample, expert evidence on the laboratory procedure, procedural challenges to the arrest or interview, or the statutory defence where it applies.
A successful trial outcome means no conviction, no disqualification, and the case is closed. An unsuccessful trial outcome means sentencing on the same day, without the early-plea credit. That is the calculus you and your solicitor work through at Step 6.
Book your free confidential consultation! →
Frequently Asked Questions
How long does the police investigation usually take?
Six to twelve weeks is typical from the date of the blood sample to the charging decision. Complex cases or laboratory backlogs can extend this to sixteen or twenty weeks. The clock starts on the day the sample is despatched, not the day of arrest.
Will I be held in a cell overnight?
Usually not. Most drug driving arrests are dealt with within six to twelve hours of arrival at the custody suite — long enough for the blood sample to be taken and for the custody sergeant to authorise bail. Overnight detention is uncommon unless there are aggravating factors such as a related offence, intoxication that prevents a sample being taken, or a refusal that needs to be processed.
Can I drive home after I’m released?
Only if bail conditions do not prohibit it. If you have been released under investigation rather than bailed, there is normally no driving restriction (the disqualification only takes effect on conviction). If a not-to-drive bail condition has been imposed, breaching it is a separate offence and will almost certainly result in remand to court.
When do I find out if I’m being charged?
You will be told the moment the police have a charging decision. If you were bailed to return to the police station, the answer comes at that return date. If you were released under investigation, a charge arrives by postal requisition through recorded delivery — usually between eight and sixteen weeks after the arrest.
Do I need a solicitor at the police station?
Yes. The duty solicitor at the custody suite is free, confidential, and independent of the police. Even if you intend to instruct privately later, the duty solicitor at interview makes a substantive difference to how the case develops. There is no advantage to declining legal advice, and every drug driving case has the right to it.
What happens if the blood test comes back below the legal limit?
You will be released with no further action and the case is closed. The arrest itself remains on the police national computer for a period under data retention rules, but there is no charge, no court appearance and no conviction. Where the reading is borderline, the police will usually consult the Crown Prosecution Service before making the charging decision.
Can I plead guilty by post for drug driving?
No. Drug driving is not eligible for the single-justice procedure (the postal-plea route used for minor offences). You must attend court in person for the first hearing. Personal attendance is one of the procedural rules that distinguishes drug driving from low-level motoring offences such as speeding.
How long does a drug driving conviction stay on my record?
The endorsement (code DG10) remains on the driver record for eleven years from the date of conviction. The criminal record is held indefinitely under the Police Act 1997 framework, although it becomes spent for most disclosure purposes after a defined rehabilitation period (currently five years for a fine and twelve months from the end of any custodial sentence). Insurance disclosure rules vary by insurer; many ask about the previous five years, some about the previous eleven.