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.
See deployment.
View, judgment, belief - takes into consideration other information in addition to observations, data, calculations, and interpretations.=
Also referenced in ANSI/ASB 167 Standard for Reporting Results from Friction Ridge Examinations.
ordinally ranked predefined verbal expressions for different degrees of strength of opinion
Note 1 to entry: See ISO 21043-4:2025, Annex B for examples of opinion scale.
the acute angle between two optic axes of a biaxial crystal.
a direction of isotropic light propagation in an anisotropic crystal. Uniaxial crystals have one optic axis; biaxial crystals have two optic axes.
determined by the relationship of the refractive indices of a material. For uniaxial crystals, if ε > ω, the crystal is positive (+); if ω > ε, the crystal is negative (-). For biaxial crystals, if γ-β > β-α, the crystal is positive (+); if γ-β < β-α, the crystal is negative (-).
Height of the surface at position (x, y).
Organization responsible for recovering organs from donors.
A method of isolating DNA from cells involving phenol and other organic chemicals.
residues from the propellant and the priming mixture that are organic compounds.
The general location where a fire or explosion began. (See Point of Origin, or Area of Origin.)
the location of the applied sample or the starting point for the chromatographic development of the applied sample.
an accurate and complete replica of the primary image, irrespective of media.
Discussion—For film and analog video, the primary image is the original image.
in forensic audio, the first manifestation of sound in a recoverable stored format.
The document or other substrate with the handwriting, machine, or other markings that caused indentation(s) on a document(s) or other substrate beneath it (the recipient document).
The Organization of Scientific Area Committees is part of an initiative by NIST and the Department of Justice to strengthen forensic science in the US. The organization is a collaborative body of more than 500 forensic science practicioners and other experts. NIST established OSAC to support the development and promulgation of forensic science consensus documentary standards and guidelines, and to ensure that a sufficient scientific basis exists for each discipline. See the OSAC website.
Technique that uses skeletal measurements and statistical models to objectively compare size and shape relationships between elements.
Ordinate values within a dataset that received an erroneous signal during the measurement and nolonger represent the real surface. These often appear as spikes in the dataset. Detection methodsinclude local slope and neighboring height thresholding.
A term used to describe a specific pattern or arrangement of design elements on an outsoletypically associated with a manufacturer and having a name and/or style number.
Any current in excess of the rated current of equipment or the ampacity of a conductor; it may result from an overload (see short circuit or ground fault).
A fire fighting term involving the process of final extinguishment after the main body of the fire has been knocked down. All traces of fire must be extinguished at this time.
Operation of equipment in excess of normal, full-load rating or of a conductor in excess of rated ampacity that, where it persists for a sufficient length of time, would cause damage or dangerous overheating. A fault, such as a short circuit or ground fault, is not an overload.
oval-shaped, heavily-pigmented inclusions usually found in the hair cortex.
the combination of one compound or element with another that involves the loss of electrons from its atomic structure.
Discussion—Oxidation and reduction always occur simultaneously (redox reactions), and the substance that gains electrons is termed the oxidizing agent.
A substance, not necessarily containing oxygen, that causes oxidation.
compounds generally containing oxygen that react vigorously with fuel compounds (reductants) thereby increasing the energy of the deflagration of the primer.
a material that releases oxygen, or that reacts readily with fuels, and enables the initiation or increased intensity of a fire or explosion.
Insufficiency of oxygen to support combustion. (See also Ventilation-Controlled Fire)
commonly known as a pigmented coating (see coating).
a pigmented coating.
The roof of the mouth separating the oral cavity from the nasal cavity. Canines have a bony hard palate and a soft tissue extension called the soft palate.
The roof of the mouth separating the oral cavity from the nasal cavity. Canines have a bony hard palate and a soft tissue extension called the soft palate.
A friction ridge image from the palm (side and underside) of the hand. A full palm printincludes the area from the wrist to the tips of the fingers.
Acronym for Palm print Acquisition Profile. It is a series of sets of progressively morestringent parameters and requirements relevant to palm print acquisition.
a type of device manufactured for the capture of account data from magnetically encoded cards that operates in-line with the original ATM, gas pump, or other card reading device.
in computer forensics, a logical portion of a media that functions as though it were physically separate from other logical portions of the media.
The application of a clear polymer coating on a document(s) within a vacuum chamber to strengthen and stabilize the document(s).
a FR search of a probe image against a database to generate a candidate list.
see passive headspace concentration.
A trained final response given by the canine that requires an inactive behavior such as sitting, staring or lying down. These types of behaviors are typically trained so as not to disturb the environment and/or forensic evidence. (See passive response, response.)
A trained final response given by the canine that requires an inactive behavior such as sitting, staring or lying down. These types of behaviors are typically trained so as not to disturb the environment and/or forensic evidence.
A trained final response given by the canine that requires an inactive behavior such as sitting, staring or lying down. These types of behaviors are typically trained so as not to disturb the environment and/or forensic evidence.
A trained final response given by the canine that requires an inactive behavior such as sitting, staring or lying down. These types of behaviors are typically trained so as not to disturb the environment and/or forensic evidence.
Any component of a building or structure that provides protection from fire or smoke without any type of system activation or movement. [3, 2018]
an extraction technique in which a portion of the headspace vapors in the sample container is concentrated onto an adsorbent medium.
A type of response that the canine displays/indicates in a manner that does not disturb the environment (i.e., sit, stand, lie quietly, or focus/stare after the detector canine has detected a trained odor). (See passive alert.)