See Why 6 Drug Driving Cases Were Dropped

A roadside swab that comes back positive or a laboratory finding showing a result "over the limit" may make a prosecution seem inevitable. However, that does not mean the outcome has already been determined. Drug driving cases depend on several forensic and procedural stages, including the roadside test, collection of the blood sample, laboratory testing, and disclosure of the evidence to the defence. If a significant problem arises at any stage, the prosecution may fall apart before a verdict is 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 show the particular issue that caused each prosecution to fail.

1. The Blood Result Fell 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 charged with the separate offence of driving while unfit through drugs. The allegation relied in part on statements he had made during a police interview several months later. Professor Atholl Johnston was instructed as an expert and concluded that the concentration identified in Mr Singh's blood did not correspond with what he had described taking and was unlikely to have had much effect on him. A separate mistake in the hospital's paperwork also formed part of the case. The prosecution eventually discontinued the proceedings.

Why this is significant: a charge does not necessarily mean that the available evidence supports the allegation. Where a result is below the legal limit, or expert analysis shows that the detected level was unlikely to affect a person's ability to drive, a prosecution resting on weaker evidence may be successfully challenged.

2. Disclosure Deadlines Were Repeatedly Missed by the Prosecution 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 together with the supporting material. That deadline passed without compliance. New directions were issued at a later hearing, but those requirements were missed as well. When the matter reached a preliminary hearing only a few weeks before the scheduled trial, the prosecution still had not supplied the required material. It then discontinued the proceedings rather than attempt to continue without its evidence being properly in order.

Why this is significant: the Criminal Procedure Rules impose genuine disclosure duties on the prosecution, including requirements about when evidence must be provided. Repeated failures to meet those obligations are not merely administrative errors. Courts have repeatedly prevented prosecutors from relying on material served too late, and that can leave the case unable to proceed.

3. The Arresting Officer's Account Could 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 displayed a "blue line" for cocaine. That description did not match the way the device indicates a positive result, since an actual positive produces two red lines. Elsewhere in the officer's evidence, there were also contradictions about which drug had allegedly produced the positive reading. Those inconsistencies became clear during cross-examination at trial. The prosecution ultimately accepted that it could no longer establish that the roadside test had been positive at all. That finding undermined the lawful basis for requiring Mr Lewis to provide a blood sample, and no further evidence was offered.

Why this is significant: roadside testing evidence, including an officer's description of what occurred, is capable of being challenged just like any other part of the prosecution case. Even apparently minor inconsistencies in the way a test result is recorded or described may become important enough to undermine the allegation.

4. The Sample Did Not Contain Enough Blood for Valid Testing R v CH, Bexley Magistrates' Court [Case Discontinued, November 2020]

Mr H arranged for part of his own blood specimen to be examined by an independent forensic toxicologist. The expert reached a clear conclusion: the quantity of blood provided was insufficient to perform a valid analysis. After that evidence was presented to the Crown Prosecution Service together with a formal defence statement, the prosecution discontinued the case roughly one week before trial.

Why this is significant: strict requirements apply to the quantity, handling, and division of blood specimens. Having the defendant's own portion independently examined may reveal defects or limitations that were not identified by the prosecution laboratory.

5. The Laboratory Lost the Required Accreditation During the Proceedings 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 analysing blood specimens had lost its UKAS accreditation for the particular tests required under section 5A of the Road Traffic Act 1988. In Mr T's case, the issue emerged only after the prosecution served its own analytical data pack and that material was examined. Once it became clear that the required accreditation had been lost, serious questions arose about the reliability of the analysis as a whole. On the trial date, the prosecution applied for an adjournment. The court refused the request, and the prosecution offered no evidence.

Why this is significant: a laboratory result showing a person to be "above the limit" depends on the reliability and proper accreditation of the laboratory that generated it. If the laboratory did not hold the appropriate accreditation for the testing undertaken, the reported figure may not withstand scrutiny in court.

6. A Genuine Medical Explanation Was Not Properly Evaluated R v Franklin, Cambridge Magistrates' Court [Case Discontinued, April 2022]

Mr Franklin was prosecuted for failing to provide a specimen after informing police that he had a needle phobia. When a person raises a possible medical reason for being unable to provide a sample, the law requires a medical professional to assess whether that reason amounts to a reasonable excuse. In Mr Franklin's case, however, no medical professional was brought in to carry out that assessment. An expert later reviewed his medical records, consulted with him, and produced a report confirming that the phobia was genuine. In light of that evidence and the procedural failure that had occurred, the prosecution discontinued the case before trial.

Why this is significant: a charge of "failure to provide" does not automatically establish an offence. Where there is a genuine medical explanation, the police must ensure that it is appropriately assessed. Failure to do so may significantly weaken the prosecution case.

What These Cases Have in Common

These six prosecutions did not end because the police simply "changed their mind." In each instance, there was a specific issue that could be identified and demonstrated, whether that involved a result below the legal limit, missed disclosure obligations, unreliable officer evidence, an insufficient blood sample, a laboratory without the necessary accreditation, or a medical explanation that had not been properly assessed. Each outcome depended on a defence team identifying the relevant weakness and knowing how to examine it.

For anyone facing a drug driving allegation, the circumstances surrounding the traffic stop, the handling of the sample, and the evidence supporting the charge can be more important than a single figure appearing on a laboratory report. Consulting a specialist solicitor at an early stage provides an opportunity to 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. The outcome of every case depends on its individual facts.