6 Drug Driving Cases That Fell Apart and the Reasons Why

A positive roadside swab or laboratory result that is "over the limit" may make a prosecution appear inevitable. That is not necessarily the case. Drug driving proceedings depend on a sequence of forensic and procedural stages, including the roadside test, blood collection, laboratory testing and disclosure to the defence. A failure at any point in that sequence can cause the prosecution to fail before a verdict is reached.

Drug Driving Solicitors has acted for clients in dozens of drug driving matters that resulted in discontinuance, dismissal or acquittal. The six examples below come from the firm's own case history and explain the precise issue that caused each prosecution to fall apart.

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

Mr Singh's case was unusual because his blood specimen was found to be below the legal limit, but he was nevertheless charged with the separate offence of driving while unfit through drugs. The allegation relied in part on comments he made during a police interview several months later. Professor Atholl Johnston was instructed as an expert and concluded that the blood level was inconsistent with the amount Mr Singh said he had taken. He also found it unlikely that the level would have had much effect on him. Alongside a separate mistake in the hospital's paperwork, this led the prosecution to discontinue the matter.

Why it matters: a charge does not itself prove that the evidence supports it. A result below the limit, or expert analysis of what a particular level would realistically mean for a person's driving ability, may defeat a case founded on weaker evidence than it initially appears to have.

2. The Laboratory Lost Its Accreditation During the Case: R v LT, Llandudno Magistrates' Court (March 2021)

A number of the firm's cases depended on the same issue: the laboratory that tested the blood sample had lost its UKAS accreditation for the particular testing required under section 5A of the Road Traffic Act 1988. In Mr T's matter, this was identified only after the prosecution served its own analytical data pack and it was examined. Once the accreditation loss had been established, the reliability of the full analysis became questionable. The prosecution sought an adjournment on the trial date, but the court declined the request and no evidence was offered.

Why it matters: an "above the limit" finding is only reliable if the laboratory producing it was properly accredited to carry out the relevant test. Without that accreditation, the figure in the report may be incapable of withstanding scrutiny in court.

3. A Genuine 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 the police that he had a needle phobia. Where a person raises a potential medical explanation for being unable to give a sample, the law requires a medical professional to consider whether it provides a reasonable excuse. In this case, no medical professional was asked to carry out that assessment. An expert report, based on Mr Franklin's medical records and a consultation with him, confirmed that the phobia was genuine. Confronted with that evidence and its own procedural failing, the prosecution discontinued the case before trial.

Why it matters: "failure to provide" does not automatically amount to an offence. Police must ensure that a genuine medical reason is appropriately assessed, and a failure to do so can weaken the prosecution's entire case.

4. The Officer's Evidence Did Not Withstand Scrutiny: R v Lewis, Manchester Magistrates' Court [Case Dismissed, February 2023]

In Mr Lewis's case, the arresting officer stated that the roadside drug test showed a "blue line" for cocaine. That is not how a positive result is displayed by that device, since a true positive produces two red lines. Elsewhere, the officer's account was also internally inconsistent about the drug for which the test was said to be positive. These contradictions emerged during cross-examination at trial. The prosecution then accepted that it could no longer establish that the roadside test had been positive, removing the legal basis for requiring a blood sample at the outset. No further evidence was offered.

Why it matters: roadside drug test results, and the officers who document them, can be challenged in the same way as any other evidence. Even apparently minor inconsistencies in an officer's description of the test can be sufficient to dismantle the prosecution.

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

After Mr Sharpe entered a not guilty plea, the court imposed a clear timetable requiring the prosecution to disclose its forensic report and supporting material. The prosecution allowed that deadline to pass. At a subsequent hearing, further directions were made, but those requirements were missed as well. When the matter came before the court for a preliminary hearing only weeks before trial, the prosecution had still not complied and discontinued rather than proceed with evidence that was not in order.

Why it matters: the Criminal Procedure Rules impose meaningful requirements on the prosecution to disclose evidence within the required time. Repeated non-compliance is not merely a technical issue. Courts have repeatedly prevented the prosecution from relying on late-disclosed material, and that may be fatal to the case.

6. There Was Insufficient Blood Available for Testing: R v CH, Bexley Magistrates' Court [Case Discontinued, November 2020]

Mr H submitted part of his own blood specimen to an independent forensic toxicologist. The expert reached a clear conclusion: the sample did not contain enough blood for a valid analysis to be performed. This was presented to the Crown Prosecution Service with a formal defence statement, and the case was discontinued around one week before the trial.

Why it matters: strict rules govern the quantity, handling and division of a blood sample. Testing an individual's own portion independently may reveal issues that the prosecution's laboratory did not identify.

What These Cases Have in Common

These six prosecutions did not end because the police "changed their mind." Each failed for a distinct and demonstrable reason: an unaccredited laboratory, missed disclosure obligations, an inadequate sample, an unassessed medical explanation, a result inconsistent with the charge, or evidence that failed under examination. In each matter, the outcome depended on a defence team knowing where to investigate.

For anyone facing a drug driving charge, the circumstances of the stop, the sample and the evidence supporting the allegation may carry considerably more weight than one laboratory figure. Obtaining advice from a specialist solicitor at an early stage provides the best opportunity to establish whether any of these issues may also apply.

This article provides general information only and is not legal advice. Every case depends on its individual facts.