How Are Expert Reports Submitted During Trials?

Expert reports are an integral part of many criminal cases in England and Wales, especially where technical, scientific or specialised knowledge is needed to understand issues that fall beyond everyday experience. Whether the topic is forensic analysis, medical opinion or digital evidence, expert reports help the court understand complex matters. This article explains how expert reports are prepared, served and used in criminal trials, the legal framework that governs them, the duties of experts, procedural requirements, and common challenges encountered in practice.

Introduction

In criminal proceedings, courts decide disputes based on evidence presented by the prosecution and defence. Sometimes the facts of the case involve issues that the judge and jury cannot assess without specialised expertise. In these situations, expert witnesses are instructed to prepare expert reports, which are written documents setting out their findings and opinions. The process of submitting these reports is governed by clear legal rules designed to ensure fairness, transparency and reliability of evidence.

What is an Expert Report?

An expert report is a written document prepared by someone qualified in a particular field (for example, forensic science, medicine, engineering or psychology) who provides an informed opinion based on evidence and relevant data. Expert reports are admissible in criminal trials if they comply with the rules on expert evidence and are relevant to an issue in dispute.

The courts allow expert evidence where it will help the judge or jury understand matters outside ordinary experience. Expert evidence may be needed to explain DNA analysis, ballistics, psychiatric assessments or other specialised fields.

Legal Framework and Duties

In criminal trials, expert evidence (including reports) is governed by the Criminal Procedure Rules (Part 19) and associated Criminal Practice Directions. Under these rules:

• Experts have an overriding duty to help the court, not just the party instructing them.
• Experts must be impartial, objective and unbiased in their opinions.
• Experts must disclose anything that could undermine their opinion or credibility.

This means experts must prepare reports that are clear, transparent and explain their reasoning in language accessible to the court. Their duty is to assist the tribunal of fact - judge or jury - by setting out opinions on matters within their expertise and explaining the factual basis for those opinions.

When Are Expert Reports Prepared?

Expert reports may be prepared at different stages of a criminal case:

• During the investigation: Police or investigators may instruct experts to examine evidence and prepare preliminary reports.
• After charge but before trial: Reports are prepared once the defence and prosecution identify issues requiring expert analysis.
• During case preparation: Experts may be asked to update or extend their reports if new information emerges.

Experts should ideally be instructed early in the process to ensure that their work informs both case preparation and disclosure obligations.

Preparing the Expert Report

When an expert is instructed, they should be given clear terms of reference outlining the specific questions on which the court requires an opinion. These instructions help shape the expert's work and ensure their report is focused on relevant issues.

Content Requirements

Under CrimPR 19.4, an expert's report must include:

1. The expert's qualifications and experience.
2. A summary of the facts and material on which the opinion is based.
3. A clear explanation of the methods and assumptions used.
4. A statement of the opinion reached and reasons for it.
5. Disclosure of any limitations, uncertainties or ranges of opinion.
6. A declaration that the expert understands and has complied with their duty to the court.
7. A statement of truth, similar to a witness statement.

The report must explain not only the expert's conclusions but also the factual premises and reasoning that support them, allowing the court and opposing party to evaluate their validity.

Service and Disclosure of Expert Reports

Expert reports must be served promptly on the court and all parties once they have been completed and before the trial. The relevant rules require that:

• The expert's report is served as soon as practicable after it is prepared.
• The party relying on the report also serves any material capable of undermining the expert's opinion (for example, alternative data or contradictory findings).
• If requested, the expert must be given reasonable opportunity to produce records of any tests, measurements or experiments underlying their opinion.

Failure to comply with service requirements can result in the court refusing to admit the report or restricting its use, unless all parties agree otherwise or the court gives permission.

The Criminal Procedure and Investigations Act 1996 also imposes broader disclosure obligations requiring investigators and the prosecution to disclose material that may assist the defence, including drafts, documents and material related to expert analysis in some cases.

Expert Proceedings and Trial Preparation

Expert reports should be considered at an early stage of trial preparation. In some cases, courts may order:

• A joint expert statement where experts from both sides agree on basic principles and identify only the factual points in dispute.
• Case conferences between experts to narrow issues and help streamline expert evidence at trial.

These measures help judges and juries focus on the genuine areas of disagreement and avoid unnecessary expert testimony that merely repeats uncontested points.

Where multiple defendants seek to rely on expert evidence on the same issue, the court can direct that a single expert give evidence to avoid duplication, or that experts be selected jointly if co‑defendants cannot agree.

Oral Evidence and Court Presentation

An expert report may be submitted even if the expert is not called to give oral evidence, but if an expert is to be relied upon at trial, the court may require them to attend and give oral testimony, especially if the report's findings will be tested under cross‑examination.

If it is proposed not to call the expert to give oral evidence, the court must grant leave (permission). In deciding whether to allow the report without oral evidence, the judge considers:

• The contents of the report.
• Why oral evidence is not required.
• Whether it would be possible to challenge the report if the expert is not present.
• Whether admitting the report without oral evidence would unfairly prejudice the accused.

Reports admitted without oral testimony remain part of the evidence open to scrutiny by defence counsel, and juries or judges will take them into account with appropriate caution.

Common Challenges and Risks

Expert reports can be challenged on several grounds:

• Procedural non‑compliance with service and disclosure rules.
• Lack of relevance or failure to address an issue genuinely in dispute.
• Insufficient qualifications or experience of the expert.
• Unreliable methodology or unsupported assumptions.

Courts may order further reports, supplementary evidence or expert conferencing to resolve these challenges.

Concerns have been expressed in recent cases about the quality and regulation of expert witnesses, and there are ongoing debates about accreditation and oversight to ensure that expert reports are consistently reliable and understood by courts.

Practical Considerations for Legal Teams

Solicitors and barristers should:

• Identify early whether expert evidence is needed and on what issues.
• Agree clear terms of reference for the expert's work.
• Ensure reports meet the content and service requirements of the rules.
• Prepare for cross‑examination of experts at trial.
• Consider joint expert statements and pre‑trial expert conferences where appropriate.

Effective preparation and management of expert reports can significantly influence trial outcomes, especially in technically complex cases.

Key Takeaways

• Expert reports are written by qualified specialists to assist the court with complex factual or technical issues.
• The Criminal Procedure Rules (Part 19) and Criminal Practice Directions govern how these reports are prepared, served and used.
• Experts owe a duty to the court and must prepare comprehensive, unbiased reports.
• Reports must be served on all parties as soon as practicable, and compliance with procedural requirements is essential.
• The court may require experts to give oral evidence or allow reports to be used without testimony with permission.
• Early and clear management of expert evidence helps ensure fair and efficient trials.