This guide is maintained as a current resource for September 2026 and covers only the laws of England and Wales. Information is for general guidance, not legal advice. Consult a qualified solicitor for advice specific to your situation.
Know the rules regarding police breathalyser tests. Learn when officers can legally request a sample, your rights if stopped, and the consequences of refusing a test under drink-driving laws.
Breath testing by police is a core part of enforcing drink‑driving laws in England and Wales. It helps officers determine whether a person has alcohol in their body above the legal limit and whether further investigation is required. This article explains the legal framework governing roadside breath tests, what police can and cannot do, what your rights are, and what can happen if you fail or refuse a test. It refers to current UK law and official guidance.
Understanding Roadside Breath Tests
A roadside breath test (also called a preliminary breath test or breathalyser) is a quick check to see if a driver has alcohol in their system. It gives an immediate result but cannot be used as evidence in court to prove an offence. If the result suggests alcohol is present above certain levels, the police will usually take you to a police station for a further, evidential breath test under controlled conditions.
Under UK law, the police have the power to require you to take a preliminary breath test only when specific legal conditions are met.
When Can Police Ask You to Take a Roadside Breath Test?
A police officer may lawfully ask you to take a roadside breath test if they reasonably suspect one of the following:
- You have been drinking alcohol and are driving, attempting to drive or are in charge of a vehicle.
- You have committed a moving traffic offence (for example, speeding, dangerous driving, or careless driving).
- You have been involved in a road accident and the officer reasonably believes you may have been driving or in charge of the vehicle at the time.
In each case, the officer must have reasonable grounds to form this suspicion. Police cannot demand a breath test at random without such grounds.
What Happens at a Roadside Breath Test?
When the police ask you to provide a sample of breath:
- You will be asked to blow into a handheld device carried in the police vehicle.
- The device gives an immediate indication of whether alcohol is present and an approximate level. This roadside reading is not evidence in court.
- If the device shows alcohol above a certain threshold or if the officer has other reasonable grounds to suspect impairment, you will usually be arrested and taken to a police station for an evidential test.
If the roadside test indicates you are not over the legal limit, the officer may permit you to continue your journey.
Legal Limits for Alcohol
Under the Road Traffic Act 1988, the legal limit for alcohol in England and Wales is:
- 35 micrograms of alcohol per 100 millilitres of breath – this is the statutory breath limit.
Police and courts often treat readings slightly above this threshold with professional judgment, but generally the evidential machine's result at the station is what matters for charging decisions.
Refusal and Failure to Provide a Breath Sample
Refusing a Roadside Breath Test
A refusal to provide a breath sample at the roadside, without a reasonable excuse, is itself a criminal offence.
A reasonable excuse might include a genuine physical or mental condition that makes it impossible to provide a sample. Medical evidence is usually required to support such a claim.
If you refuse without a reasonable excuse, the police can arrest you and require an evidential specimen at the station.
Failure to Provide at the Police Station
Once arrested, you will be asked to provide an evidential specimen (usually breath, but blood or urine may be requested if breath cannot be provided). Refusing without a valid excuse is a serious offence under the Road Traffic Act 1988 and carries the same penalties as a drink‑driving conviction.
Consequences of Failing or Refusing a Test
If You Fail the Test
Failing an evidential breath test (that is, registering above the legal limit) at the police station generally leads to:
- Criminal charges for driving or attempting to drive while over the prescribed limit.
- A mandatory driving ban of at least 12 months for a first offence (longer for repeat offences).
- An unlimited fine and up to six months' imprisonment, depending on circumstances and sentencing.
- The conviction will be endorsed on your driving licence and can affect employment and travel.
If You Refuse Without a Reasonable Excuse
Refusal to provide a specimen (breath, blood or urine) even at the station is treated as a separate offence of failure to provide. This offence carries similar penalties to exceeding the drink‑drive limit, including a minimum 12‑month ban, an unlimited fine and possible imprisonment.
What Are Your Rights?
- You must comply with a lawful request for a breath test when the legal conditions are met.
- You have the right to ask for medical assistance or an explanation if you are unsure whether you can provide a sample because of a health condition; but you must not refuse without a reasonable excuse.
- You can request to contact a solicitor or family member after arrest. This should happen once you are detained at the station.
- If you believe the test was conducted improperly (for example, the device was faulty), this may be a ground to challenge evidence in court.
Practical Examples
- Example 1: An officer stops you after a minor collision and asks you for a roadside breath test. You provide a sample that indicates alcohol is present. You will likely be taken to the station for an evidential breath test. If that test confirms you are over the limit, you will be charged.
- Example 2: You refuse a roadside breath test stating you cannot provide a sample, but no reasonable medical explanation exists. You can be arrested, and failure to provide will result in a separate offence with significant consequences.
Key Takeaways
Roadside breath tests are a lawful tool for police to identify potential drink‑driving. They are only permitted when an officer reasonably suspects you have consumed alcohol, committed a traffic offence, or been in an accident. Refusing or failing to provide a breath sample without a reasonable excuse is a criminal offence and will likely result in arrest and significant penalties. Compliance with the legal framework helps ensure a fair process and accurate evidence if charges follow.
