Begin preparing for accident reconstruction by gathering information about what materials already exist and where they are held. You do not need to reconstruct the entire incident yourself. A brief case description, a list of documents and the questions the technical analysis should answer will be useful. This guide concerns preparing material after an incident, once rescue operations and activities at the scene have ended.
Make an inventory of available documentation
ENFSI guidelines identify the importance of scene documentation, accounts, photographs and an accident description. Incomplete data may need to be supplemented before reconstruction. At the first contact, it is therefore useful to distinguish clearly between material you hold and material whose existence you merely know about. [1]
Include available reports, sketches, photographs, recordings, vehicle damage documentation and earlier studies in your inventory. State whether you have the complete document or only selected pages. If an authority is handling the case, provide the case reference and stage of proceedings. Do not send the entire case file immediately: the material to be shared should be matched to the questions and agreed form of cooperation.
Preserve photograph and recording provenance
For each collection, add who created it, when it was obtained and what it shows. Separate photographs from the accident scene from later workshop photographs and images taken after repairs. If you do not know the date, write ‘date not established’. This prevents the order of files in a folder from being mistaken for the sequence of events.
For CCTV, SWGDE recommends acquiring a recording as close to the source recording as possible. Exporting to another format may reduce the quality or scope of the data. Establish whether a file from the recorder is available, rather than only a video showing playback on a screen. If you have such a copy, preserve it and describe its origin. [2]
Do not trim your only version of a video down to a few seconds. You can give the time of the relevant excerpt in a separate note. If the camera clock differed from the actual time, report this without changing the timestamps in the file yourself. Any acquisition of material from a surveillance system administrator should be agreed with an authorised person.
Prepare a brief timeline and mark uncertainties
Describe, in order: the participants’ directions of travel, observed manoeuvres, the moment of vehicle contact and their positions after the incident. For each point, give the source: your own observation, a photograph, recording or document. If participants describe the event differently, present their versions separately.
For example: ‘In photograph no. 4, the vehicle is standing by the right-hand edge of the carriageway; I do not know whether it had been moved beforehand.’ This information allows the right question to be asked. ‘The vehicle stopped at the exact point of collision’ would introduce an assumption requiring confirmation. Uncertainty should not be replaced with a categorical description.
How can your own sketch help?
A simple sketch can help explain which road section, lane or direction is involved. Mark it as an illustrative drawing made from memory. Add street names, directions and vehicle labels consistent with your description. If measurements were not taken, do not add distances based on impressions.
A client's sketch and an online map serve a supporting role. Agree with the expert whether the particular question requires measurements, inspection documentation or additional photographs. Do not re-enact manoeuvres in road traffic or collect data yourself in a way that requires entering the carriageway.
Prepare questions that can be verified
- Does the available material allow the vehicle’s path before the collision to be established?
- Do the location and nature of the damage match the described contact configuration?
- What data is missing for assessing speed or visibility?
- How would the findings change under the two specified versions of the incident?
Analysis of recordings, visibility and calculation uncertainty are among the areas described by the Institute of Forensic Research. This shows why an assignment should be narrowed to a specific technical issue. [3] Legal assessments, including the liability of those involved, remain separate.
Also state any important deadline and whether a vehicle or storage media can be made available if needed. Describe the case and available materials. An initial assessment of these allows the actual scope of further work to be established.
Sources
- ENFSI, Best Practice Manual for Road Accident Reconstruction, version 1, November 2015, chapters 8–11.
- SWGDE, Best Practices for Data Acquisition from Digital Video Recorders, 17-V-002, version 1.4, chapters 2, 5 and 10.
- Institute of Forensic Research, Road Accident Investigation Department, examination scope and research directions.
Sources accessed: 23 October 2026.