6 Drug Driving Prosecutions That Collapsed and Why

A positive roadside swab or a laboratory result showing a driver was "over the limit" can make a prosecution seem settled from the outset. In reality, it is not. Drug driving cases depend on a sequence of forensic and procedural stages, including the roadside test, collection of the blood sample, laboratory analysis, and disclosure of the evidence to the defence. If one part of that process is defective, the prosecution may fall apart before a verdict is ever reached.

Drug Driving Solicitors has acted for clients in dozens of drug driving matters that concluded with discontinuance, dismissal, or acquittal. The following six examples come from the firm's own case history and illustrate the particular issue that caused each prosecution to fail.

1. The Officer's Account of the Roadside Test Was Inconsistent R v Lewis, Manchester Magistrates' Court [Case Dismissed, February 2023]

In Mr Lewis's case, the arresting officer stated that the roadside drug test displayed a "blue line" for cocaine. That description did not correspond with the way a positive result appears on the device, because an actual positive result produces two red lines. The officer's statement also contained a separate contradiction about which drug the test had supposedly detected. During cross-examination at trial, those inconsistencies were brought to light. The prosecution then accepted that it could no longer establish that the roadside test had been positive, undermining the lawful basis for requiring a blood specimen in the first place. No further evidence was offered.

Why it matters: roadside testing and the police evidence recording those results are open to challenge just like other forms of evidence. Even apparently minor inconsistencies in an officer's description of the test can weaken the prosecution to the point that the case cannot continue.

2. A Valid Medical Explanation Was Not Properly Considered R v Franklin, Cambridge Magistrates' Court [Case Discontinued, April 2022]

Mr Franklin faced a charge of failing to provide a specimen after informing police that he suffered from a needle phobia. Where a person raises a possible medical explanation for being unable to provide a sample, the law requires a medical professional to assess whether that condition amounts to a reasonable excuse. No medical professional was called to carry out that assessment in his case. An expert later reviewed his medical records, consulted with him, and confirmed that the phobia was genuine. In light of that evidence and the earlier procedural failure, the prosecution discontinued the case before trial.

Why it matters: a failure to provide a specimen does not automatically establish an offence. When a genuine medical explanation is raised, the police must ensure it is properly assessed. Failing to do so can seriously undermine the prosecution.

3. The Laboratory Lost the Required Accreditation R v LT, Llandudno Magistrates' Court (March 2021)

A number of the firm's cases were affected by the discovery that the laboratory responsible for examining blood samples had lost its UKAS accreditation for the specific testing required under section 5A of the Road Traffic Act 1988. In Mr T's case, the issue only became apparent after the prosecution served its analytical data pack and that material was reviewed. Once it was established that the laboratory no longer held the necessary accreditation, the dependability of the analysis itself was called into question. On the trial date, the prosecution sought an adjournment, but the court refused the request and no evidence was offered.

Why it matters: an "above the limit" figure depends on the reliability and status of the laboratory responsible for producing it. If the laboratory was not properly accredited to conduct the required analysis, the reported result may be incapable of withstanding scrutiny in court.

4. The Blood Sample Was Too Small for Valid Testing R v CH, Bexley Magistrates' Court [Case Discontinued, November 2020]

Mr H arranged for his own portion of the blood specimen to be examined by an independent forensic toxicologist. The expert reached a clear conclusion: the sample did not contain enough blood for a valid analysis to be performed. After this finding was presented to the Crown Prosecution Service together with a formal defence statement, the prosecution discontinued the case approximately one week before the scheduled trial.

Why it matters: strict requirements apply to the amount, handling, and division of blood samples. Having the defendant's own portion independently analysed can reveal defects that were not identified by the prosecution laboratory.

5. The Prosecution Failed to Meet Its Disclosure Timetable Mr Sharpe [Case Discontinued, October 2018]

After Mr Sharpe pleaded not guilty, the court imposed a timetable requiring the prosecution to provide its forensic report and the material supporting it. The deadline passed without compliance. Further directions were then issued at another hearing, but those requirements were also missed. When the matter returned for a preliminary hearing only weeks before trial, the prosecution had still not complied with the disclosure timetable and chose to discontinue rather than proceed without its evidence properly in order.

Why it matters: the Criminal Procedure Rules impose genuine duties on the prosecution to disclose evidence within the required timescale. Repeated non-compliance is not merely procedural housekeeping. Courts have refused permission for evidence served too late to be relied upon, and that can leave the prosecution unable to prove its case.

6. The Blood Result Was Below the Legal Limit R v Singh, Swindon Magistrates' Court [Case Discontinued, December 2022]

Mr Singh's case involved an unusual set of circumstances. His blood specimen was found to be below the legal limit, but he was nevertheless prosecuted for the separate offence of driving while unfit through drugs. Part of the case relied on comments he had made during a police interview conducted months later. Professor Atholl Johnston was instructed as an expert and concluded that the concentration identified in Mr Singh's blood did not match what he had described taking and was unlikely to have had much effect on him. Together with a separate mistake in the hospital paperwork, that expert evidence ultimately led the prosecution to discontinue the case.

Why it matters: the existence of a charge does not necessarily mean the evidence supports the allegation. A result below the legal limit, or expert analysis of what a detected level would realistically mean for a person's driving ability, may undermine a case founded on evidence that is less secure than it initially appears.

What These Cases Had in Common

These six prosecutions did not end because the police simply "changed their mind." Each case depended on an identifiable and demonstrable problem: a laboratory without the required accreditation, an inadequately assessed medical reason, insufficient blood for testing, missed disclosure obligations, a result that did not support the charge, or evidence that failed under examination. In every instance, the outcome depended on a defence team knowing which parts of the prosecution case required closer scrutiny.

Anyone facing a drug driving allegation may find that the circumstances of the stop, the handling of the specimen, and the evidence supporting the charge are more important than a single figure recorded on a laboratory report. Consulting a specialist solicitor at an early stage can help establish whether similar evidential or procedural issues may be relevant to the case.

This article provides general information only and should not be treated as legal advice. Each case depends on its individual facts.