Clifford v Hertfordshire Constabulary

Expert opinion evidence should be admitted only where it is relevant to an issue in the proceedings. Even relevant evidence may be excluded where its cost and the time required are disproportionate to its likely benefit. Where the issue is a factual question about what an investigator was told, expert evidence obtained years later cannot assist in determining the true state of affairs. The court may decide the necessity and admissibility of expert evidence at an interlocutory case-management hearing rather than defer the issue to the trial judge. Disclosure disputes must also be managed proportionately, particularly where the pleaded issues are narrow.

The claimant brought proceedings against the Chief Constable alleging malicious prosecution and misfeasance in public office after criminal proceedings concerning indecent images were discontinued following his acquittal. The re-amended claim focused on whether an investigating officer had been told, before the prosecution decision, that the images had been found in temporary or recovered folders, and whether the prosecution should consequently have been instituted or ended earlier.

The parties made interlocutory applications concerning expert computer evidence and specific disclosure. The defendant sought to rely on expert opinion evidence, while the claimant argued that expert evidence was unnecessary and that the issues were factual.

1. Expert evidence. Expert evidence should be adduced at trial only if it is relevant to an issue between the parties. Even where it has peripheral relevance, the court may exclude it under its case-management powers if the cost and time involved would be disproportionate to the benefit likely to be obtained.
2. The central issue was whether the investigating officer had been informed of the location of the images before the decision to prosecute, or failed to act promptly after receiving that information. That was a pure issue of fact to be determined by factual evidence. Expert opinion obtained years after the events could not assist in resolving it.
3. The claimant’s credibility was not a central issue on the pleaded case. The defendant did not allege that the claimant had actually downloaded the material, but that the officers reasonably suspected that he had done so. The investigating officers and the computer examiner already had relevant expertise, and their factual evidence was sufficient to address the issues.
4. The issue of expert-evidence admissibility had been squarely raised at the interlocutory hearing. There was no good reason to postpone its determination until trial. The defendant was therefore precluded from relying on Mr Fellows’s expert opinion, although he could give relevant factual evidence if properly identified.
5. Disclosure. The dispute over disclosure appeared disproportionate to the narrow issues remaining in the claim. A further supervisory hearing was directed, with provision for the court to inspect documents withheld on grounds of legal professional privilege or public interest immunity if necessary. If no suitable hearing date could be obtained, the disclosure issue was to be remitted to a Master.