Civil and criminal matters · England and Wales
Single Joint Expert for civil and criminal digital evidence
Alistair Ewing considers Single Joint Expert instructions for digital evidence, subject to conflict checks, a suitable scope and the court’s directions. Compute Forensics is partnered with Audio Video Forensics Ltd for matters that also need specialist examination of sound or images.
Independent opinions · Defined responsibilities · Coordinated evidence handling
At a glance
- A Single Joint Expert is instructed on an issue for more than one party under the applicable procedure.
- In criminal proceedings, the specific joint-expert rules concern co-defendants.
- Digital forensics examines the file, device and handling history; audio and video specialists examine the recorded content.
- Each expert identifies their own work, opinion and limits. A shared project does not automatically become a Single Joint Expert appointment.
How do joint expert instructions differ in civil and criminal cases?
Single Joint Expert in a civil claim
Under CPR Part 35, a Single Joint Expert prepares a report for the court on behalf of two or more parties, including the claimant. The court may direct one expert to address a particular issue. Instructions from a relevant party must be copied to the other relevant parties.
The court considers proportionality, complexity and whether a joint instruction would help resolve the issue efficiently. A defined question about a file’s history, a device record or an agreed dataset may be suitable. The appointment and permitted issues depend on the case and court order. See CPR 35.2, 35.7 and 35.8 and Practice Direction 35, paragraph 7.
Single Joint Expert in a criminal case
Criminal Procedure Rules 19.7 and 19.8 allow the court to direct one expert where more than one defendant wants expert evidence on an issue at trial. Each instructing co-defendant may send instructions and must copy them to the other co-defendants.
This is a co-defendant arrangement. It does not automatically create a joint prosecution-and-defence instruction. Separately instructed experts may also discuss their evidence and prepare a joint statement under rule 19.6; that is a different process. See the current Criminal Procedure Rules, Part 19.
For wider context, read about digital evidence in civil litigation or criminal defence digital evidence. The instructing lawyers confirm the appropriate route, permissions and directions.
Our partnership with Audio Video Forensics
How do digital forensics and audio/video analysis work together?
A recording can raise two questions at once: what happened to the file, and what can reliably be heard or seen? Compute Forensics and Audio Video Forensics bring these strands together through an agreed division of work. The scope identifies which specialist addresses each question and any overlap that needs checking.
| Evidence question | Compute Forensics: digital evidence | Audio Video Forensics: recorded content |
|---|---|---|
| Where did the recording come from? | Examine available native files, device or account records, metadata and transfer history. Identify what the available copy can establish. | Assess the supplied recording and identify the source quality, completeness and additional material needed for the audiovisual questions. |
| Could a discontinuity be an edit? | Check file structure, encoding, packet timing and software indicators. Consider export, conversion and recording behaviour. | Examine speech, background sound, waveforms, spectrograms and picture continuity around the disputed point. |
| What can be heard or seen? | Preserve the received file and document the relationship between it and working copies or extracted frames. | Assess intelligibility and image detail; undertake suitable enhancement, transcription or comparison within the agreed scope. |
| Do the sources fit the same timeline? | Compare file and system times, account activity and relevant device records, including time-zone and clock uncertainties. | Compare observable events and audiovisual timing across recordings. Explain the basis of any synchronisation or sequence. |
| How should the findings be presented? | Explain the technical observations, methods, provenance limits and supporting records. | Explain the sound and image analysis, processing applied and limits of any enhanced exhibit or interpretation. |
AVF’s published services include audio analysis and enhancement and video analysis and enhancement. Availability and the right specialist are confirmed at scoping. Enhancement can make existing information easier to examine; it cannot be assumed to recover detail that was never recorded.
Anonymised experience
Examples of work with Audio Video Forensics
These examples describe complementary technical work. They do not claim a Single Joint Expert appointment or a particular court outcome.
A disputed mobile video recording
In a criminal defence instruction, Alistair examined the supplied video file’s metadata, internal structure, encoded timing and selected picture changes. AVF separately examined the audiovisual content through critical listening, waveform and spectrogram review, and frame-by-frame inspection.
The two strands addressed the recording at different levels. A change in sound or viewpoint could be compared with the way the file stored and timed the media. Each examination retained its own scope and limitations; a technical test of the supplied copy could not establish the full history of an unavailable original device.
Authentication of a supplied event recording
AVF examined a video supplied for authentication and prepared enhanced material. Alistair prepared a technical report with supporting data and extracted frames for review. The work also identified questions about the recording device, the original file and how the circulated copy had been transferred or processed.
This combination connected the interpretation of the pictures and sound with the history of the evidence supplied. The distinction between a source recording, a circulated clip and a processed exhibit helped frame what could be assessed and what further material was needed.
Can the specialists share a brief or produce one report?
A common evidence schedule and coordinated questions can reduce repeated handling and keep the work focused. The letter of instruction should identify each expert, their discipline, the material they receive and the questions they will answer.
The reporting arrangement is then agreed with the lawyers and, where required, the court. Separate signed reports may be appropriate. Any combined document must make authorship, examinations and responsibility for each opinion clear. One contact or one evidence package does not turn two specialists into one appointed expert.
Where opinions differ, the difference and its reasons should remain visible. The purpose of coordination is to help the court understand the evidence, not to require a common conclusion.
What helps avoid duplicated work?
- Define the disputed proposition. For example: whether the supplied clip supports a claim of continuous recording, or whether a particular passage can be transcribed reliably.
- Agree the source set. Identify originals, exports, enhanced copies and missing material. Give each item a consistent reference.
- Allocate the questions. Separate file examination from content analysis and record any deliberate cross-checks.
- Use a shared timeline. Specify whether a reference means playback time, a frame number, embedded time or real-world time.
- Report the limits. Explain unavailable sources, processing effects and reasonable alternative explanations alongside the findings.
What should a solicitor send for an initial estimate?
- Party names for conflict checks, jurisdiction and the proposed type of instruction.
- The issue to be answered and any court order defining the expert evidence.
- A list of devices, files or accounts, with approximate volumes and recording durations.
- Whether native files, original devices and prior reports are available.
- Reporting and hearing dates, funding arrangements and whether audiovisual support is needed.
Use the first enquiry to describe the matter without attaching evidence. A written scope identifies the work, specialist involvement, fees and secure transfer arrangements. See expert witness fees and estimates and quality standards and data handling.
If the main task is finding and collecting records across several systems, the eDiscovery data-sources guide can help prepare the source list.
Discuss the expert arrangement your case needs
Start with the disputed question, the available sources and the deadline. Alistair will assess the digital evidence scope and whether AVF input would help.