The Reliability of Image Representation

It’s been a long time since I posted here.
I am the first one to admit that I can get a little passionate about Forensic Video Analysis and CCTV Investigation, and my frustrations with various aspects of this niche field of forensics can take their toll on my wellbeing.
Sometimes you just have to take a breath, rather than bang your head harder on the brick wall.

There are though a handful of other analysts who have continued to shout about certain issues for some considerable time. Unfortunately, we often seem to get drowned out and the problems get lost and ignored within the legal system. It was a refreshing change therefore a few weeks ago, to see and hear from one of those respected colleagues on the UK’s Channel 4 news.

It is clear that the news item has probably been heavily edited, cut down and slanted to concentrate on facial analysis BUT there are some important takeaways from this and things that we, as analysts, must consider.

Firstly, let me make this clear. CCTV is not putting innocent people behind bars.
Misunderstanding, incorrect handling, poor analysis and biased presentation will put innocent people behind bars. It’s not CCTV’s fault!

Second.. the images and comparative analysis displayed in this video leave a lot to be desired and cause damage to the role of the Forensic Video Analyst…but worryingly, I have seen worse.

Professor Gillian Tully, right at the outset states, “When it comes to the interpretation of CCTV Images, its difficult for us at the moment to have the assurance that it’s done properly across the board…” She then goes onto the fact that people and organisations do not meet the required standards set by the Forensic Science Regulator (FSR).

I am not going to get into the huge mess surrounding the initial setting of the FSR’s guidance in the UK.

I am not going to get into the conflicts between the FSR’s guidance, the training delivered to most police organisations in Forensic Video Analysis, and then the guidance documents published by the National Police Chiefs Council.

I am also not going to get into the ISO accreditation of video units and private service providers and the difficulties this has caused…

We have to go all the way back to the start, and clearly define what a person should do and what is their role to the court.

I have been lucky, or unlucky in many cases, to review lots of Forensic Video and Image reports and there are some constant problems. The most common is an unclear definition of what that person’s role is within the investigation.

In any case where video evidence is to be used, whether that from CCTV, Cellphones or Body Worn Video, an analyst must ensure and report on the integrity of that video, the authenticity of that video and the reliability of the image representation.

Why is an expert in video required to do this? You all watch the TV, you all watch YouTube. The latest viral video of a dog skiing is completely different, however, to a piece of footage recorded on a CCTV system that could result in an innocent person being convicted of a crime they did not commit.

Regardless of the task or question being asked, the analyst has a duty to the court to assess and understand the evidence.

The analyst’s first responsibility is to identify any changes in the image since the time it was first created. This ensures the integrity of the exhibit. Any changes must adhere to a scientific workflow and therefore be repeatable, reproducible and explainable. Any item produced as a result of a change will differ from the original and, as such, will be a new exhibit. Any undocumented changes must be disclosed as these will affect the integrity of the produced item.

The second responsibility is to ensure authenticity. Any item must be a true and accurate representation of that which it purports to be. The video may not be authentic in its original state. The capture and encoding of the video may have changed the shape, dimensions, speed or colour, and consequently, anything in the scene would suffer from this incorrect view. Authenticity therefore not only relates to the identification of fabricated evidence, either through malcous manipulation or incompetence, but more commonly to the method of aquisition. In these cases, authenticity can often be restored through restoration and enhancement.

This is where the third responsibility comes in. Ensuring the reliability of the image representation. This is often termed the scientific stage, as processing, reconstruction, testing, restoring, enhancing, collating, annotating and presenting video evidence must adhere to a scientific workflow. If those are followed, and any required peer review completed, the produced item or presented fact should be reliable.

It is not the analyst’s role to form an opinion as to an item, or a mark. It is an analysts role to inform the judge or jury that the item or mark constructed within the image is reliable and can be trusted.

It is not the analysts role to make up terms and use incorrect, unscientific procedures.

It is not the analyst’s role to fit the narrative of those who are employing them.

Comparative Video and Image Analysis can be extremely time-consuming work…. but also very frustrating. Most CCTV used is not installed for the purpose it is being used for and, as such, identifying and documenting the limitations is key for transparency and trust.

When the analysis starts with the identification of the facts, it is easy to perform unbiased analysis and, if necessary, report that an object or views representation is unreliable.

And this workflow is not just for comparative analysis. Timelines, storyboards and the tracking of persons through scenes can all be presented incorrectly with unreliable visual information if the original data is not understood and analyzed correctly first. The staged disclosure of video exhibits is also of key importance to reduce unconcious bias.

An analyst is there to identify the facts in the video or image. There should be very little subjective interpretation. The facts are presented after objective analysis.
If an analyst analyzes a video and is able to confirm though reconstruction and restoration that an object or person has a number of atributes then those atributes are facts.

However, an analysts most important skill is the ability to identify features that are not reliable or that contrast, rather than compare with a known object or person.

I am sure that Reuben could have said a lot more (I imagine there was a lot edited), but the report has highlighted the scary fact that there are people in the UK and around the world presenting this sort of stuff and they are full of unreliable images caused by a lack of understanding and questionable terms to baffle a jury.

The more times that things like this get shouted about, the better it will be for Forensic Video Analysis and the legal system.



This was a great find by Larry over at media-geek

Forevid appears to be great little tool for small video jobs. I have only had a quick look around so far but it would suit specialised viewing teams thanks to it’s easy GUI.
Take a look at

A full review with some ideas on workflow coming soon.