OSAC Lexicon
The OSAC Lexicon is a compendium of forensic science terms and definitions. This terminology tool was created to help bring consistency and understanding to the way terms are used by the various forensic science. Use of the OSAC Lexicon does not replace the need to reference the original published source.
The terms and definitions in the OSAC Lexicon come from the published literature, including documentary standards and technical reports. It is continually updated with the latest work from OSAC units, as well as terms from newly published documentary standards and standards elevated to the OSAC Registry.
Gradually terms are evaluated and harmonized by the OSAC to a single term. This process results in an OSAC Preferred Term. An OSAC Preferred Term is a term, along with its definition, that has undergone review and evaluation by the FSSB Terminology Task Group and has been approved by the FSSB. The FSSB recommends that subcommittees use OSAC Preferred Terms when drafting standards.
The OSAC Lexicon should be the primary resource for terminology and used when drafting and editing forensic science standards and other OSAC work products.
degree of color distinction (color contrast) between colors within a soil are categorized as faint, distinct and prominent.
Discussion—Within this practice, these contrast classes are used to describe the degree of color distinction between two evidentiary soil samples, whereas the United States Department of Agriculture – National Resource Conservation Service – National Cooperative Soil Survey (NCSS) uses these contrast classes to describe color distinction within soil horizons. Faint color contrast is evident only on close examination. Distinct color contrast is readily seen but contrasts only moderately with the color to which it is compared. Prominent indicates colors which contrast strongly with the color to which it is compared; prominent colors are commonly the most obvious color feature of the section described. The NCSS thresholds between faint and distinct color contrast (1) are adapted as exclusion criteria in forensic comparisons of soil.
See gamut
Capable of undergoing combustion.
any substance that will burn, regardless of its autoignition temperature, or whether it is a solid, liquid or gas.
capable of undergoing combustion.
Any finely divided solid material that is 420 microns or smaller in diameter (material passing a U.S. No. 40 Standard Sieve) and presents a fire or explosion hazard when dispersed and ignited in air.
An instrument that samples air and indicates whether there are ignitible vapors or gases present.
Any liquid that has a closed-cup flash point at or above 37.8C (100F). (See also 3.3.89, Flammable Liquid.)
See Ignitable Liquid
A chemical process of oxidation that occurs at a rate fast enough to produce heat and usually light in the form of either a glow or flame.
a usually rapid chemical process (such as oxidation) that produces heat and usually light.
a usually rapid chemical process (as oxidation) that produces heat and usually light.
the heat, gases, volatilized liquids and solids, particulate matter, and ash generated by combustion.
Discussion—Combustion products are the result of complete or incomplete combustion, but not thermal decomposition (see pyrolysis).
The heat, gases, volatilized liquids and solids, particulate matter, and ash generated by combustion.
A simple file format for tabular data where individual values are separated by a comma (or other designated delimiter).
The intermixing of biological material representing multiple individuals.
particles have compositions that are also commonly found in environmental particles from numerous sources.
Discussion—When present in addition to particles that are characteristic of, or consistent with, GSR, or both, these particles can be of use in the interpretation of a population of particles and, consequently, the likelihood that that population is GSR. In isolation, however, such particles have little use in examinations for GSR.
An algorithm that allows signals with a large dynamic range to be transmitted overfacilities with a smaller dynamic range. It is used in telephony (see -law and A-law)and some other types of communications
An identification technique involving the direct comparison of antemortem and postmortem medical imaging to include radiographs, computed tomography (CT), magnetic resonance imaging (MRI) and other modalities.
A qualitative conclusion of any comparison performed to assess the degree of similarity or difference between DNA data (e.g., inclusion or exclusion).
The process of examining two or more DNA data sets to assess the degree of similarity or difference.
The process of examining two or more DNA data sets to assess the degree of similarity or difference.
The process of examining two or more DNA data sets to assess the degree of similarity or difference.
Consists of an examination of correspondence or non-correspondence between items, unknown and known.
The search for and detection of similarities and dissimilarities in observed data between friction ridge impressions.
The search for and detection of similarities and dissimilarities in observed data between friction ridge impressions.
The search for and detection of similarities and dissimilarities in observed data between friction ridge impressions.
A series of computational steps which seeks to assess both the level of geometric similarity (similarity of toolmarks) and the degree of certainty that the observed similarity results from a common origin. A comparison algorithm makes use of a scoring function or similarity score.
a system of two microscopes positioned side-by-side and connected via an optical bridge so that two specimens are examined simultaneously in a single field of view in either transmitted or reflected light.
fire debris, (1) a sample of material collected from a fire scene which is, to the best of the collector's knowledge, similar with respect to relevant characteristics to a sample suspected of containing ignitable substance, but which is not expected to contain an ignitable substance; (2) a sample of suspected ignitable substance submitted for the purpose of comparing with any ignitable substance separated from a debris sample.
Discussion—A comparison sample should not be confused with a control sample. For example, a comparison sample might include unburned carpet or flooring that meets the requirements in (1).
Discussion—Although, in theory, the use of comparison samples can help clarify the presence of a suspected inherent ignitable liquid, the presence of an ignitable liquid in a comparison sample does not necessarily mean it is inherent to the material.
Software that implements a comparison algorithm and may also include database, search, and visualization functionality.
any variety of optical devices that can be placed in the light path of a polarized light microscope to introduce known, fixed or variable retardation in a specific vibration direction; the retardation and sign of elongation of the fiber can then be determined.
a compensator (usually a plate of gypsum, selenite or quartz) that introduces a fixed retardation between 530 to 550nm (approximately the retardation of the first order red color on the Michel-Levy chart).
a compensator (usually a mica plate) that introduces a fixed retardation between ~137–147nm (approximately the retardation of first-order gray on the Michel-Levy chart).
a wedge, usually cut from quartz, having continuously variable retardation extending over several orders (usually 3 to7) of interference colors.
a quarter-wave plate inserted above the specimen in the parallel "0" position with a calibrated rotating analyzer; measures low retardation and requires the use of monochromatic light.
a compensator typically containing a plate of calcite or quartz, which can be tilted by means of a calibrated drum to introduce incrementally variable retardation.
demonstration that a forensic science practitioner has acquired and demonstrated specialized knowledge, skills, and abilities (KSAs) in the standard practices necessary to conduct examinations in a discipline or category of testing prior to performing independent casework
The demonstration of technical skills and knowledge necessary to perform forensic DNA analysis successfully.
Demonstrated and documented ability of an individual to perform assigned work in a discipline or subdiscipline, in accordance with a laboratory's technical procedures and training manuals, before the performance of independent casework.
demonstration that a forensic science practitioner has acquired and demonstrated specialized knowledge, skills, and abilities (KSAs) in the standard practices necessary to conduct examinations in a discipline or category of testing prior to performing independent casework.
demonstration that a forensic science practitioner has acquired and demonstrated specialized knowledge, skills, and abilities (KSAs) in the standard practices necessary to conduct examinations in a discipline or category of testing prior to performing independent casework
Possessing and demonstrating the requisite knowledge, skills, and abilities to successfully perform a specific task.
A test designed to establish that an individual has demonstrated achievement of technical skills and met minimum standards of knowledge necessary to perform forensic DNA analysis.
Evaluation of a persons knowledge and ability to perform work before authorization to do so independently.
Also referenced in ANSI/ASB Standard 099 Standard for Footwear/Tire Examination Proficiency Testing Program.
A test used to demonstrate an individual's ability to successfully conduct an examination(s) prior toperforming casework.
A person having suitable or sufficient skill, knowledge, experience to train canines and canine handlers.
A person having suitable or sufficient skill, knowledge, experience to train canines and canine handlers.
A person having suitable or sufficient skill, knowledge, and experience to train canines and canine handlers, who has demonstrated, through education, training, and operational experience, extensive skills and knowledge in the subject field or discipline. This person would normally perform the maintenance training and proficiency training in the field and may train canines in preparation for a formal course of instruction.