What is Digital Image Comparison?

Digital image or video comparison compares known and unknown subjects, vehicles, or objects depicted in digital imagery. What makes it a forensic image comparison to be used in a courtroom? The application of a widely accepted, objective, unbiased methodology to compare images. Subsequently, we identify whether an unknown subject matches the known subject. 

In addition, we can also perform comparison services from image files extracted from video recordings like CCTV video evidence. These services assist criminal defense cases, law enforcement applications, and litigation. In fact, our comparison services solved a real case of mistaken identity

We take pride in our ability to teach our clients, and the court, to answer difficult questions, truthfully.

A digital image comparison or video comparison investigation is only successful with high quality images. A wide variety of digital camera systems and formats can create these images. As a result, sufficient image quality is necessary to analyze and extract characteristics for photo forensics analysis. See an example of imagery considered adequate and insufficient for forensic image comparison below.

Insufficient for Identification

Sufficient for Identification

video comparison

Image Comparison from Video Evidence

The most prolific source of police evidence is video images. However, video is not an accurate medium for identification on its own. For example, video images taken from surveillance recordings may not be authentic for identifying a subject. 

Compression artifacts will reduce the accuracy of the specific details necessary to identify a suspect or vehicle. In fact, some cases where information that the surveillance camera didn’t initially record in the video images was added. And so, an expert must be able to interpret data to provide an accurate comparison.


Primeau Forensics applies the ACE-VR methodology to all image comparison investigations. This method ensures, without a doubt the accuracy of the results through repeatable processes.


First, we evaluate the quality/clarity of the input images. These criteria include the resolution, frame rate, compression artifacts, bit rate, lighting, and more. For example, if our experts have a clear picture to extract data from, they can proceed. On the other hand, image quality may be insufficient based on the cameras and lenses. Thus, a conclusion can be drawn as such.


Next, we prepare the images for the comparison tool. In any case, Image comparison is a two-step process. First, a thorough examination of class and individual characteristics between the known and unknown allows an analyst to form an opinion. Second, if the objects or subjects in question are the same, they can be identified to the exclusion of all others.


The visual quality of the evidence, present characteristics, and undefined differences all play a role in making conclusions. As such, our experts utilize a scale commonly known as the "likelihood scale" or the "scale of conclusions." At this point the scale describes the strength of our opinions coupled with the comparison investigation. Although this confidence scale originated in the United Kingdom, experts now use it internationally in forensic image comparison investigations.


At this point, all comparison investigations are peer-reviewed by a colleague of similar training and experience. In fact, peer review is completed internally within our firm or externally by an expert at another firm. The peer-reviewed conclusions are thus strengthened when reviewed and verified by another expert. Again, this process is critical to protecting the accuracy of the investigation.


Finally, investigative information including the request, methodology, comparison charts, opinions, and peer review, are drafted into an expert report. Reports are only generated at the request of the client's attorney. Therefore, our reports must outline the request if the request was fulfilled and the methodology followed. This ensures it can be considered admissible evidence through repeatability.







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Expert witness services are available for image comparison investigations by Primeau Forensics. Our expert witness services include a forensic report of all our testing, trial preparation, and testimony. These opinions can assist the trier of fact in determining the identification of subjects, objects, or vehicles without a doubt.

We have helped legal teams in courtrooms across the USA and can provide expertise to create a successful litigation plan. As a result, our trial experience makes us stand out from other companies.

audio forensic expert