Physical Fit / Fracture Match Analysis

Contributed by Troy Nowak

Fracture match examinations are conducted to show the realignment of two or more objects to prove that they at one time formed a single object.

There are several types of materials fracture match examinations can be useful in:

  • Glass (in a breaking and entering)
  • Metal (forced entry with a tool)
  • Wood (assault with baseball bat)
  • Plastic materials (to include wrappers, bags, etc)
  • Paint (hit and run)
  • Tape (binding)
  • Certain criteria must be met for fracture match examinations to be conducted. Obviously the item(s) must be broken and detached, then the items must be capable of being physically realigned (perhaps a portion is missing, can it be found), do the items fit together as a “lock and key” like a jigsaw puzzle (surface markings may exist on the item that align and look for an edge to edge boarder), and are the pieces unique (can they be interchanged with similar pieces elsewhere).

    There are 3 dimensions (depth and edges) to a separation; each dimension of the separation should be examined.

    Class and individual characteristics must be observed for a conclusion to be drawn in a fracture match examination and the examiner must be familiar with class and individual characteristics:

  • Class Characteristics are those characteristics that make items similar at best – for example, color, shape, pattern. Measurable features of a specimen resulting from design factors, these are determined prior to manufacture.
  • Individual Characteristics are those characteristics that make items unique – for example, accidental surface markings due to wear or use. In an uncontrolled environment, the physics (torque, acceleration, force, speed) behind the random force used to break or tear an item are not reproducible.
  • Why conduct a fracture match examination? These types of examination can be a positive form of identification. One item can be associated to another item to the exclusion of all others; meaning that an item did not originate from any other source.

    So what differentiates a skilled forensic examiner from the casual observer? One must have experience, the ability to recognize the criteria for a fracture match, the ability to distinguish between class and individual characteristics, and an understanding of the scientific method.