Evidence on Video
Traditional investigations will typically rely on the available physical evidence, statements from witnesses, and educated analysis. An investigation will try and piece together events that led to the issue at hand. In the case of fire investigations, we will look at burn patterns to determine the origin and more detailed analysis to determine the cause. In the case of motor vehicle accident reconstruction, we will look at damage patterns, skid marks, and do computer or mathematical analysis to determine speeds or conditions prior to a crash.
A recent surge in video surveillance including doorbell cams on houses, dash cams in cars, traffic cameras, and security cameras means there is a greater chance that the incident of interest was recorded. But a video must be weighed against other physical evidence and only considered as part of the overall investigation.
Video can be useful for fire investigation. If a neighbour records a fire from a doorbell camera, the area where the fire is first seen is useful to help determine the origin of the fire. The video could also capture an arson in progress. Although, a video recording is not always a ‘smoking gun’. A man seen running into a house with a gas can from a neighbour’s doorbell camera is not conclusively an arson case if it can be shown that the fire started from a faulty power bar and no accelerants were found. But then if burn trailers are found from the door to various rooms in the house and heavy accelerants are found, the video provides further proof to reinforce the findings.
Dashcams in vehicles are also becoming more prevalent as people wish to record their travels. The video from these dashcams can be a useful part of an accident reconstruction investigation. Many cameras are equipped with GPS sensors and embed location and speed data into the video. As with the information from a Crash Data Recorder (black box), the GPS data in a video must also be weighed against other physical evidence. A GPS registers its location by triangulating from multiple satellites on a period basis, generally once per second. Each location measurement has an accuracy that can vary by 1 or 2 metres. The speed is determined by calculating the distance between two location measurements and the time between each measurement. Therefore, the speed shown by a GPS unit is the average speed from the previous time sample and has a location error for each measurement. The GPS speed is not an accurate real-time measurement. However, the speed recorded by the GPS is fairly reliable with a constant steady speed. The location errors average out over time and a steady speed is well represented. This can be a reliable part of the evidence that could differentiate between a 50 km/hr impact and an 80 km/hr impact.
In addition to the GPS data, the video itself can be an excellent record of the events. Witness statements are often unreliable due to perspective and opinions. A witness can state that a vehicle was travelling ‘very fast’ when it was actually doing the speed limit, or ‘I didn’t see the car until it was 5 feet away’ when it was actually 100 feet. Having a video recording removes all the issues with guessing and memory problems. But again, the video must only be taken as a piece of the puzzle and should be used in conjunction with other physical evidence.
Video recordings are becoming more prevalent with the surge of fixed cameras and mobile phones. Locating a video may require further investigation work including canvassing of neighbours or witnesses, but a video can be a very useful piece of evidence for many investigations. But the investigator must also weigh the contents of a recording with other physical evidence.
