Forensic Image Comparison Services

Forensic Image Comparison Services

Forensic image comparison or forensic image comparison is the process of comparing object(s) or persons(s) when at least one of the items in question is captured in imagery, and making an assessment of the correspondence between features of the captured imagery for rendering an opinion regarding identification or elimination (as opposed to a demonstrative exhibit). Examples of photographic comparisons include, but are not limited to:

  1. A facial comparison between an unknown subject depicted in a surveillance image with an identified suspect.
  2. The comparison of objects such as vehicles depicted in surveillance images with those recovered in an investigation.

Any methodology applied to photographic comparison should incorporate an analysis of the imagery, a comparison of individual features, an evaluation of the significance of the comparison and a verification of the comparison.

-SWGDE Guidelines for Forensic Image Analysis PG 6

The Scientific Methodology


  • Analysis
  • Comparison
  • Evaluation
  • Verification
  • Report

Quality of Images for Comparison

In order to accurately interpret the content of an image under examination, it is imperative that the examiner recognize the conditions and limitations that occurred during image capture, processing or editing. Imaging conditions can impact the appearance of subjects or objects depicted. Important conditions to understand include, but are not limited to:

  • Resolution
  • Frame Rate
  • Bit Rate
  • Perspective Changes
  • Compression Artifacts
  • Optical Defects
  • Sensor Defects
  • Lighting Conditions
  • Motion or Focal Blur

Images used for Comparison from Video

It is considered that today, the most prolific source of evidence for police is from video images. Video is not an accurate medium for identification on its own. This is because digital compression removes and adds information that wasn’t originally included. When the objects or people displayed in the video images aren’t clear, we will perform a forensic video enhancement investigation. This may become necessary in order to see the details of the images more clearly. The video enhancement process will also reinforce the accuracy of the comparison investigation.

Exemplar VS Evidence

Evidence: Images or videos that contain objects or people that are considered UNKNOWN

Exemplar: Images or videos that contain objects or people that are considered KNOWN

Comparison Criteria

These images must be compared using acceptable best practices approved by the scientific community. These best practices include the acceptable criteria for comparison. The criteria are divided into two categories, class characteristics and individual characteristics.

Class characteristics: A class characteristic is an identifiable feature that assists in narrowing the statistical probability that a questioned object or person belongs to the same group as a known object or person that shares the same feature. Consistent class characteristics between questioned objects and individuals can only suggest similarities. They cannot, by themselves, be used to infer a positive identification.

Individual Characteristics: Class characteristics are the observable characteristics which are used to divide objects into groups or classes through the sharing of common features. A correspondence of class characteristics may be useful for grouping subjects. Likewise, a discordance of class characteristics can be used to eliminate potential subjects.

A thorough examination of class characteristics and individual characteristics contrasted and compared between questioned and known objects or persons may allow an experienced and properly qualified analyst to form an opinion. If it is safe to do so, the objects are one in the same, eliminating all others of the same class.

The image comparison criteria is defined by the standards presented by SWGDE (Scientific Working Group on Digital Evidence) as well as LEVA (Law Enforcement and Emergency Services Video Association).

Expert Witness Testimony

It is our responsibility as an expert witness  to present observations in a simple unbiased nature to the trier of fact. When we write our reports, we ensure that the foundation our opinions formulate from is scientific. This gives the testimony and report integrity, therefore making it “bulletproof” if you will.  In other words, we do not generate opinions about the likelihood of objects or people based on subjective reasoning, but rather scientific analysis.

If identification of a specific type of vehicle is needed, an automotive expert can be retained. Involving another forensic science can strengthen an investigation by supplying additional identification information. This strengthens our reports as well as our testimony.

Client Reviews

As a business owner myself, I am aware of the effort it takes to assemble a team of employees that conduct their business as if it were their own, and take pride in how they represent your company to others. As an owner who feels has achieved that status myself, I immediately recognize it in others. I must say that this is not common in the workforce today. From the first contact with your company, through closeout, every one of your employees made this experience a pleasure and acted with the upmost more
Abc Def
20:32 03 Dec 18
Primeau Forensics is a professional, top-flight organization that knows how to access and deliver verifiable forensics information quickly, efficiently and productively. Don't let their cheerful, friendly attitude make you think they are not on top of their game--they are!read more
dan schulte
18:35 12 Dec 18
I received credentials from two technicians, then a third person ended up doing all the work and kept in touch with me by e-mail. I never saw any proof that the work was done and they told me they found nothing. They could not tell me what was making the noise or the lights. A waste of $ more
Teresa Galyon
16:13 13 Dec 18
Excellent work. Primeau took a low light camera recording of vandalism at my home and converted the video to images that we used to identity the vandals. Additionally, Primeau was able to identify characteristics of the vandals car that were used for a positive identification. Services were efficient, timely, and professionalread more
Todd Conte
15:18 27 Aug 18
Ed and his team are great! I took in footage of my boyfriends dog being stolen and they were so willing to take every step possible to enhance the video to retrieve the information we needed. The resolution on our camera/video wasn't great (our fault, not theirs) and they were unable to get the information we needed BUT they guided me in the next steps to take. Thank you guys!!read more
Anita Tela
12:47 23 Oct 17

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