Forensic image comparison is the process of comparing objects or people when at least one variable is captured in imagery, and making an assessment of the correspondence between features of the captured imagery regarding identification or elimination.
Here are a couple examples of forensic image comparison:
In order to accurately interpret the content of an image under examination, it is critical that the expert evaluates and recognizes the conditions and limitations that occurred during image capture, processing or editing. Every condition can impact the appearance of subjects or objects depicted. Important conditions to understand include, but are not limited to:
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
Images must be compared using the accepted 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.
A thorough examination of class characteristics and individual characteristics compared and contrasted between questioned and known objects/persons may allow an experienced and properly qualified analyst to form an opinion. If it is safe to do so, the objects are the same, eliminating all others of the same class.
The image comparison criteria are defined by the standards presented by SWGDE (Scientific Working Group on Digital Evidence) as well as LEVA (Law Enforcement and Emergency Services Video Association)