Can I Be Charged If I’m in a Public Car Park and Not on the Road?

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One of the most common questions drivers ask after an incident—or even routine police contact—is whether they can be charged under the Road Traffic Act while stationary in a public place such as a car park. This question becomes even trickier when we involve substances like cannabis, due to confusing legal limits and testing methods.

In this article, we break down the key legal points related to being “in charge” in a public car park scenario, explain how THC blood limits interact with impairment, and clarify the difference between a roadside swab test and the police station blood test. We’ll also consider the risks associated with downtime during EV charging—something drivers of electric vehicles from EV Powered might find especially relevant.
Understanding the Legal Framework: What Is “In Charge”?
The essential offence here is being “in charge of a motor vehicle in a public place” while unfit through drink or drugs. The core legislation is Section 4 of the Road Traffic Act 1988. It doesn’t matter if you are on the road or stationary; the law covers all public places, and many public car parks fall into this category.
What is a “Public Place”?
"Public place" is broadly defined by legislation and judicial interpretation. Typically, a public car park owned by a local authority or open for public use is considered a public place. This means even if your car is stationary and the engine is off, you can still be considered “in charge” under the law.
Key point: The vehicle doesn’t need to be moving. Being behind the wheel with the keys in your pocket — common when charging an EV — still counts. Private driveways or car parks that aren’t open to the public usually do not count. Case Example:
A driver stopped at an EV charging station in an NHS England car park leaves the keys in their pocket while waiting 20 minutes for their car to charge. Police approach, suspecting drug use. Under Section 4, this driver can be charged for being in charge while unfit if evidence of THC or other drugs is found, even though the vehicle was stationary and engine off.
THC Blood Limits vs Impairment: What You Need to Know
The legislation sets specific blood limits for certain drugs, including THC— the active ingredient in cannabis. The limits are very low and designed for public safety, but they don’t always correlate with impairment. This distinction is critical in both roadside stops and police station tests.
Substance Specified Limit in Blood Relation to Impairment THC 2 micrograms per litre Does not necessarily confirm impairment
This means a driver could test over the limit without necessarily being impaired in a way which affects driving performance. However, the law does not require proving impairment for Section 4 offences—it’s enough that the concentration exceeds the limit.

This contrasts with the statutory medical defence, which can help if you have evidence that you used the drug for medical purposes https://bizzmarkblog.com/what-if-i-am-charging-at-home-on-my-driveway-does-in-charge-apply/ under guidance from the General Medical Council (GMC) or NHS England rules, and you were not impaired.
Roadside Swab Test vs Police Station Blood Test
Police use different forms of drug testing depending on the situation:
Roadside swab test: A quick saliva test designed to detect the presence of certain drugs in the mouth. It is a preliminary check but cannot alone prove the offence. Police station blood test: The definitive test for drug levels in the blood, including THC concentration. This sample is analysed in a laboratory and forms the core evidence in prosecutions.
The important point is that the roadside swab alone cannot lead to a conviction. It triggers the need for a station blood test if positive. Drivers should understand that refusing the blood test is a separate offence and can lead to serious penalties.
Scenario: Keys in Pocket at EV Charger
Imagine you're charging your EV and the keys are in your pocket. A roadside swab test returns a positive result for THC. You’re taken to the https://dlf-ne.org/what-is-the-biggest-mistake-prescribed-patients-make-at-charge-points/ https://dlf-ne.org/what-is-the-biggest-mistake-prescribed-patients-make-at-charge-points/ police station for a blood test showing THC above the legal limit.

Despite being stationary in a public car park with the engine off, you can still be prosecuted for "in charge" under Section 4 because of the legal definition of “public place” and “in charge.” This scenario underscores the importance of understanding the charging downtime window as a legal risk period.
EV Charging Downtime: A Legal Risk Window
As electric vehicles become more common, drivers can find themselves parked for extended periods—sometimes with the engine off—while their EV charges. EV Powered have highlighted that this downtime might lull drivers into a false sense of security regarding the law.

Remember:
The vehicle must be safely parked and not just left with the keys nearby if you want to avoid charges. Being “in charge” includes having easy access to the vehicle, which usually means keys in your possession. Delays at chargers cause longer exposure to police checks; any drugs actively in your system can lead to positive roadside tests.
This means that planning for post-driving drug use or ensuring you aren’t carrying active substances during charging is a wise precaution. The statutory medical defence and appropriate prescription evidence from a GMC-regulated clinician can be crucial here, especially if you have medicinal cannabis prescribed by NHS England.
Statutory Medical Defence & Burden of Evidence
The law allows for a statutory medical defence if you can prove:
You consumed the drug under medical advice and held a valid prescription. The drug did not affect your ability to drive safely. You complied with GMC and NHS England prescribing standards.
However, the burden of evidence is on the driver to provide this proof. Simply saying "I'm prescribed cannabis oil" is not enough; documentation and possibly expert testimony might be required.
Key Takeaways Section 4 applies if you are in charge of a vehicle in a public place, even if stationary in a car park. THC blood limits set fixed concentration levels that don’t necessarily correlate with impairment but still trigger offence. Roadside swab tests trigger the need for blood tests, which provide the legally admissible evidence for prosecution. EV charging downtime is a risk window—keys in pocket and engine off doesn’t prevent charges. The statutory medical defence requires strong, documented evidence from GMC-regulated prescribers and NHS England compliance. Final Advice
If you find yourself in a public car park and questioned by police about drugs or alcohol:
Remember Section 4 of the Road Traffic Act 1988: being “in charge” covers stationary situations in public places, including car parks. Do not rely on myths: “Engine off means I can’t be done” is incorrect and a dangerous assumption. Cooperate respectfully with roadside swab tests: refusal leads to separate offences. Request and provide medical evidence: if you have a genuine clinical prescription from GMC-regulated doctors or NHS England pathways, ensure you have it ready.
Understanding these points can help drivers avoid unfortunate legal pitfalls, and for those using medicinal cannabis, ensure they take the necessary steps to prove compliance with the law.

If you need more information about roadside procedures or medical defences, consulting specialists familiar with public place road traffic act offences is highly recommended.
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