Common Terms

Bulk sample - A sample that is large enough to weigh.

Class characteristics - Measurable features of a specimen which indicate a restricted group source, but not traceable to an individual person or item. Class characteristics can determine things like automotive paint types, blood types of people or a collection of new Phillips head screwdrivers, but cannot produce a specific match or individual identification. This type of evidence may be used to narrow down a list of possible sources.

Fracture Match (sometimes called a Physical Match) - The examination of two or more objects either through physical, optical, or photographic means which permits conclusions as to whether or not the objects were either one original piece or were held or bonded together in a unique arrangement. The concept is similar to putting together the pieces of a jigsaw puzzle.

Glass - an inorganic product of fusion, cooled to a rigid condition. It is essentially composed by heating a mix of sand, limestone and soda, along with various impurities.

Individual Characteristics - Evidence that can be associated with a common source with a high degree of certainty. The probability the specimens are of common origin is so high as to defy mathematical calculations. Evidence associated with individual characteristics include fingerprints, DNA and striations on a bullet.

Microscopy - the use of or investigation with a microscope.

Reference Sample - A material of known physical characteristics authenticated by a certified procedure accompanied by or traceable to documentation.

Probative - potentially valuable and worthy of further testing and analysis evidence.

Pyrolysis - The decomposition of organic matter by heat.

Scanning electron microscope - type of electron microscope, designed for directly studying the surfaces of solid objects. This process produces a three-dimensional image of the surface of the object.

Paint - a manufactured liquid that dries to form a thin, hard coating. It is composed of carriers, pigments, modifiers, extenders and binders.

Primary transfer - The direct transfer of trace evidence from one object to another.

Radial fractures - A crack in a glass that extends outward like a spoke of a wheel from the point at which the glass was struck.

Soil profile - A vertical section through a soil showing the different horizons from the surface to the underlying parent material.

Trace sample - An amount so small that it cannot be weighed—although it may well be possible to establish its weight by means of quantitative chemical analysis.

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