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.
The testimony made by a qualified person about a scientific, technical, or professional issue. An expert is often called upon to testify due to his/her familiarity with the subject or special training in the field.
A coherent, scientifically sound statement or statements regarding the meaning of analytical findings in a forensic case that is formulated from a consideration of the synthesis of analytical data, pre-analytical factors, case history, and other relevant information
A material with a pressure ratio (maximum pressure/pressure at ignition, in absolute units) equal to or greater than 2.0 in any test when tested using the explosibility or Go/No-Go screening test described in Section 13 of ASTM E1226, Standard Test Method for Explosibility of Dust Clouds. [68, 2018]
The sudden conversion of potential energy (chemical or mechanical) into kinetic energy with the production and release of gases under pressure, or the release of gas under pressure. These high-pressure gases then do mechanical work such as moving, changing, or shattering nearby materials.
the sudden conversion of potential energy (chemical or mechanical) into kinetic energy with the production and release of gases under pressure, or the release of gas under pressure; these high-pressure gases then do mechanical work such as moving, changing, or shattering nearby materials.
Study of how chemistry, physics, fire science, engineering disciplines of fluid and solid mechanics, and heat transfer interact to influence explosion behavior.
Study of how chemistry, physics, fire science, engineering disciplines of fluid and solid mechanics, and heat transfer interact to influence explosion behavior.
Any chemical compound, mixture, or device that functions by explosion.
a single substance, or a mixture of substances, that is capable of producing an explosion upon initiation (see high explosives and low explosives).
a single chemical compound that can produce an explosion.
Any material that can act as fuel for an explosion.
a mixture of separate fuel and oxidizer components that together can produce an explosion.
the detection, identification, on-site evaluation, rendering safe, recovery, and final disposal of unexploded explosive ordnance; it may also include explosive ordnance which has become hazardous by damage or deterioration.
Discussion—1) This term is also sometimes colloquially applied to the same actions applied to improvised explosive devices (IEDs). (2) The term “render safe” involves procedures utilized by EOD technicians or bomb technicians to make an explosive device safe.
A chemical substance that can be utilized in the production of explosives by either mixing or blending with other substances, or by chemical processing. The vast majority of chemicals are used for legitimate purposes. However, some chemicals could potentially be misused for the illicit manufacture of homemade or improvised explosive. Indeed, relatively small amounts of select chemicals can be applied in certain processes that produce a significant amount of explosives.
material remaining from an explosive deflagration or detonation or from direct contact with an explosive. Explosive residue generally does not have a discernible morphology, can be visible or non-visible, and can contain uninitiated and post-combustion components.
Discussion—Visible explosive residue can be present in large (grams) and small (single particle or single crystal) quantities.
an arrangement of explosive components by which the initial force from the primer is transmitted and intensified until it reaches and detonates the main explosive composition.
A canine trained to detect and alert to the presence of explosives and explosives related substances (e.g., propellants, oxidizers, precursors) for which it has been trained that may be located in the environment.
A canine trained to detect and alert to the presence of explosives and explosives related substances (e.g., propellants, oxidizers, precursors) for which it has been trained that may be located in the environment and/or person borne.
See download
The side of a structural assembly or object that is directly exposed to the fire.
The parameter, associated with the assessment method used, that characterizes the dispersion of the values that could reasonably be attributed to the measurand.
Physical assessment of the decedent by a medicolegal death investigator.
Diagnostic medical procedure conducted by a pathologist or other specially trained medical personnel that consists of physical inspection of the decedent without internal examination; can include ancillary tests.
An evaluation of practitioner performance against pre-established criteria by means of interlaboratory comparisons. [ISO/IEC 17043:2010]
the condition in which a birefringent particle appears dark when viewed between crossed polarizers.
Discussion—Most fibers exhibit extinction when their long axis is oriented parallel to the privileged direction of one of the polarizing filters.
A procedure where the reinforcement of a previously reinforced behavior is discontinued with the intention to reduce the occurrence of that behavior
To cause to cease burning.
Total cellular DNA isolated from a biological sample to include nuclear and mitochondrial DNA.
any plot of signal intensity observed at a chosen m/z value or set of values in a series of mass spectra recorded as a function of time.
any method of exporting data from a source.
material originating from a source other than the specimen.
An estimation of a drug concentration (e.g., ethanol) at a time other than the time of sample collection. There are two types of extrpolation: back [retrograde] and forward [anterograde] extrapolation
a class of smokeless powders produced by an extrusion process where the final grain morphologies are disc or cylinder.
Organization responsible for recovering corneas/eyes from donors.
in textiles, a planar structure consisting of yarns or fibers.
in facial identification, the automated determination of the presence of human faces in digital images.
in facial identification, (1) by automated systems, the automated searching of a facial image as a probe in a facial recognition system (one-to-many), typically resulting in a group (candidate list) of facial images being returned to a human operator in ranked order based on system-evaluated similarity; (2) by humans, the mental process by which an observer identifies a person as being one they have seen before.
An investigative technique combining anatomical knowledge, artistic capability, and forensic anthropological evidence to render an estimate of an individuals facial appearance in life.
An investigative technique combining anatomical knowledge, artistic capability, and forensic anthropological evidence to render an estimate of an individual’s facial appearance in life.
in facial identification, a manual process to identify similarities or dissimilarities between two (or more) facial images or facial image(s) and a live subject for the purpose of determining if they represent the same person or different person.
gross features considered in virtually all comparisons.
in facial identification, a formal systematic facial comparison.
the discipline of image-based comparisons of human facial features.
in facial identification, the process of collecting a biometric sample from an individual by means of a sensor.
the process of landmarking defined anthropological points.
See face recognition.
in facial identification, an adjudication of a candidate list.
A positive control (see 3.7) or negative control (see 3.6) that produces an unexpected result.