Fracture matching
Fracture matching is a forensic technique used to analyze the torn or broken edges of materials to determine their origins and establish connections to potential suspects in criminal investigations. This method is particularly useful when evidence is found in fragmented states, such as broken glass, ripped cloth, or damaged tools. Forensic scientists inspect the unique characteristics of fractured edges, including their composition, surface irregularities, and the shape of the break, to piece together evidence like a puzzle. Notably, the uniqueness of each fracture means that no two breaks occur in the same way, which enhances the reliability of fracture matching in court.
This technique can be applied to various materials, including glass, metal, cloth, and plastic, and can involve both two-dimensional and three-dimensional analysis. A significant aspect of glass fracture matching is the presence of Wallner lines, which help forensic experts align broken pieces accurately. Additionally, tools used in crimes can leave distinctive metal shavings, allowing for matching of the shavings to specific tools. Fracture matching has proven instrumental in resolving complex cases, as demonstrated in instances where connections between evidence found at a crime scene and a suspect’s property have led to successful convictions.
On this Page
Subject Terms
Fracture matching
DEFINITION: Inspection of the torn or broken edges of pieces of evidence to match the edges to their sources.
SIGNIFICANCE: In some cases, pieces of evidence found at crime scenes are not in their original states, having been broken, torn, or otherwise separated from other pieces. By matching the edges of two or more pieces of broken or torn material, forensic scientists may be able to determine the origins of these pieces of evidence and thus link them to possible suspects.
Fracture matching is similar to putting pieces of a puzzle together. Anything that can be broken, torn, or otherwise separated can be subjected to fracture matching. Forensic scientists are called upon to perform fracture matching with many different kinds of materials, including glass, cloth, metal, paint, paper, plastic, tape, and wood. Matching a bullet to the gun from which it was fired is considered a special kind of fracture matching.
The combination of the composition of an object and the force used to separate it into pieces results in unique characteristics. For example, a piece of cloth, when ripped or cut, will never be ripped or cut apart in the same way twice. The cloth will have slight flaws that will span the rip or cut, and the force applied to separate it into different pieces can never be repeated identically. Because of these unique qualities, evidence of matched fractures is considered very strong scientific evidence in court.
In successful fracture matching, the broken pieces of an object can be realigned along the fracture point, and the fit of the broken pieces can be verified by markings on the surface or inside the broken object. Fracture matching can be done two-dimensionally, such as with cloth, paper, or tape, or three-dimensionally, such as with glass, metal, plastic, or wood. Investigators try to match fractures based on the chemical composition of the object, irregularities on the surface of the object, the shape of the break, and similarities between pieces of the object in age, deformation, or texture. Often, microscopic examination of the materials is necessary to determine the tiny matches in a fractured object.
Glass is a special material in terms of fracture matching; it is usually quite easy to match broken pieces of glass back together. The ridges that are formed in glass when it is broken (Wallner lines) are nearly always aligned to curve toward the point of impact. It is relatively easy for forensic scientists to use these ridges to match pieces of broken glass.
Tools can present another special kind of fracture-matching task. When metal tools are used with force against surfaces, such as to pry open windows or locked drawers, small shavings of metal from the tools are often left behind. Forensic scientists can match the markings seen on such small shavings against particular tools to determine whether those tools were used at certain crime scenes.
Fracture matching has provided important evidence in some seemingly unsolvable cases. For example, in a Florida case, a body that had been wrapped in sheets and taped with masking tape was found, and a was apprehended. A forensic scientist was able to fracture match one end of the masking tape found on the body with the corresponding end of a roll of masking tape found in the suspect’s home. Based on this and other corroborating evidence, the suspect was convicted of the murder.
Bibliography
Fisher, Barry, David Fisher, and Jason Kolowski. Forensics Demystified: A Self-Teaching Guide. New York: McGraw-Hill, 2007.
Gardner, Ross M. Practical Crime Scene Processing and Investigation. Boca Raton, Fla.: CRC Press, 2005.
Kramer, Robert E. "Case Solved with Aid of Fracture Match." Iowa Division of the International Association for Identification, 2024, www.iowaiai.org/case-solved-with-aid-of-fracture-match. Accessed 14 Aug. 2024.
Mozayani, Ashraf, and Carla Noziglia, eds. The Forensic Laboratory Handbook: Procedures and Practice. Totowa, N.J.: Humana Press, 2006.
Nowak, Troy. "Physical Fit/Fracture Match Analysis." American Society of Trace Evidence Examiners, 2024, www.asteetrace.org/fracture. Accessed 14 Aug. 2024.