Video Forensics – Case study from our archive

By | 22nd August 2014

cctv camerasWe process video evidence for the legal profession and other investigation agencies. Detailed below is a brief outline of a case we worked on some years ago.

CCTV Violent Street Brawl

A number of persons were involved in an incident in the street. Several CCTV cameras recorded the activity prior to and after the police arrived. Several uniformed police officers were deployed to restore order and detain multiple offenders.

The defendants claimed that certain officers lied about what happened. It was their belief that the CCTV evidence would support those claims by showing that some of the officers could not have seen or done what they claimed in their statements because they were elsewhere at the material times.

Our task was to identify and assign unique markers to each of the police officers seen in the CCTV footage and track their progress from their arrival until all of the offenders had been detained and taken away.

We were supplied with several video evidence exhibits on time-lapse videotape and on disc together with head and shoulders photographs identifying each police officer.

Making Sense Of The Evidence

On first sight the CCTV footage was very confusing. There were many camera angles showing police officers in very similar looking clothing chasing and detaining several offenders. The fast moving incident was covered by multiple CCTV cameras positioned around the area. There was a combination of analogue multiplexed and digital CCTV footage which had been acquired on several different source exhibits. Some of the cameras were controlled by an operator with pan tilt and zoom function. Other cameras were static. The incident was spread over a wide area with vehicles, buildings and street furniture blocking the available view in some places.

After logging all of the evidence we transferred the images onto a computer system designed for processing video evidence. It was evident that the time of day recorded by each CCTV system did not match the others. Using the main imagery from the local authority CCTV system as a reference we were able to calculate the offset for each system and synchronise the activity to +/- 1 second.

We created a ‘reference profile’ noting the appearance of each police officer when first seen. All the officers were in uniform and wearing high visibility clothing. However, there were differences including gender, physical build, shoes or boots, the position of their pocket radio and other equipment, badges and the design of the hi-vis jacket or bib. We then assigned a numbered marker to each officer and their reference profile. The CCTV images were compared to the supplied photos allowing us to put a name to each profile.

By working through the footage frame-by-frame we were able to overlay a numbered, coloured marker onto each officer. The marker was animated to track each subject’s movement on the various CCTV recordings.¬†From time to time officers grouped together, crossed each other’s path and then separated again or simply disappeared from view behind obstructions etc. Often it was necessary to work backwards through the footage and/or compare images from different angles to ascertain the correct identity for a particular individual.

Producing Clear And Factual Exhibits

The exhibit we produced was a standard DVD Video disc with a simple menu which was easy to operate. The DVD contained a compilation of the video evidence from various source exhibits. Individual cameras could be selected and played on demand either with or without the animated markers overlaid.

Video evidence is incredibly useful in many criminal and other investigations. However, sometimes the evidence is confusing for the viewer or happens so quickly that it’s difficult to establish exactly what happened with certainty. In this case our exhibit made it possible to identify and see the position of each officer at any point during the incident and therefore verify the accuracy of the accounts given in their statements.

You can find out more information by contacting us or viewing our Forensic Video Services page.

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