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 quality of a canine to persist at a task regardless of the environmental distractions or task difficulty.
Other terms specific to firearms, such as rifle, shotgun, pistol, revolver, firearm, single action, double action, sear, and cock are described in Association of Firearm and Tool Mark Examiners, Glossary [7] and Glossary-SAAMI [1]23].
an unsaturated hydrocarbon occurring in most essential oils and oleoresins of plants.
determination of one or more characteristics according to a procedure.
To discharge a firearm in a laboratory or controlled setting in order to obtain representative bulletsand cartridge cases for comparison or analysis, or to determine functionality of the firearm.
An impression made from a known footwear or tire used as an aid for comparison purposes.
a definitive procedure that produces a test result.
A term intended to encompass any report containing the description of items submitted to a laboratory, as well as any results of testing and examinations that may have occurred.
The determination, by technical means, of properties, performance or elements of materials, products, services, systems, or environments, which may involve application of established scientific principles and procedures. Testing typically applies to materials, products or processes.
See plume
The increase in length, volume, or surface area of a body with rise in temperature.
The properties of a material that characterize its rate of surface temperature rise when exposed to heat; related to the product of the material's thermal conductivity (k), its density (_), and its heat capacity (c).
A skeletal defect produced by exposure to high temperature or direct contact with flame.
a mixture comprised of a metal oxide and powdered metal that reacts with extremely high temperature and produces molten metal and slag.
Discussion—The most common thermite mixture is composed of iron oxide and powdered aluminum.
The branch of physics that deals with the relationship between heat and other forms of energy.
The study of the science, methodology, and practice of temperature measurement.
a synthetic material that softens or melts at high temperatures.
Plastic materials that soften and melt under exposure to heat and can reach a flowable state.
Plastic materials that are hardened into a permanent shape in the manufacturing process and are not commonly subject to softening when heated; typically form char in a fire.
A method for calculating match probabilities, first described by Balding and Nichols (1994), to allow for population structure in the population for which a frequency database is constructed. It allows match probabilities for subpopulations to be calculated from whole population allele frequencies. It avoids the need to assume Hardy-Weinberg equilibrium at the whole-population level.
Distance from one surface of a tape, backing, or adhesive to the other, usually expressed in the United States as thousandths of an inch, or the industrial vernacular as "mils" which represents thousandths of an inch (that is, 1 mil = 0.001 in.).
the optical path through a fiber used for the calculation of birefringence.
in facial identification, images used in facial recognition (FR) or facial identification (FI) that were not captured by the agency performing the comparison (for example, family snapshots of a missing person).
a slender strong strand or cord made by plying or twisting yarns, typically used for stitching.
An impression made on surfaces such as soil, sand, snow or mud with dimensions of length, width, and depth.
a value, based on a background sample study, below which the number of pGSR particles identified cannot be distinguished from background levels and thus cannot be reliably interpreted as associated with the discharge of a firearm or contact with a source of pGSR.
DetectionThe minimum and maximum concentration of a chemical vapor that can be detected by a canine or an instrument. BehavioralThe level of stimulation above or below which learning and/or performance is impaired.
Graphic representation of the events in a fire incident displayed in chronological order.
a electronic device used to correct timing inconsistencies, stabilize, and synchronize video signals for optimum quality.
process by which images are recorded at less than the standard rate of frames per second (National Television System Committee (NTSC) 29.97; Phase Alternating Line (PAL) 25.00) thus extending the period of time that can be covered by the storage medium.
in video analysis, a feature of digital video recorders (DVRs) that allows the equipment to adhere to data retention policies that may be mandated in certain parts of the world which results in video data becoming inaccessible after a certain date.
process of relating images, audio, or other data to one another in a chronologically ordered succession.
in computer forensics, a point in time with respect to system time used by a file system to annotate creation, access or modification of file system objects.
the most distal end of a hair shaft.
the most distal end of a hair shaft.
Organization responsible for recovering tissues from tissue donors.
Any solid biological specimen that is generally weighed for analysis (e.g., brain, liver, muscle, hair, bone, meconium).
See vaccine titer.
See vaccine titer.
The allowable range of deviation from the class resolution, symmetric around the classresolution value. For PIV single fingerprint scanners with the class resolution of 500 ppi,the tolerance is 2%. For all scanners other than PIV, the tolerance is 1%.
A measurement of an objects surface geometry. Topographic data may be one, two, or three dimensional.
1D topography data is also known as a Linear Profile. A linear profile with n points shall be represented as a function of a single coordinate where at each point along a single axis (xi) (where i=1,...,n) there is a measured height (zi). Both xi and zi are measured in standard units (e.g., micrometers). An example of a linear profile is a cross-section through a striated toolmark (e.g., bullet land area); where xi is a spatial position measured in micrometers and zi is the corresponding height of the striation profile measured in micrometers.
2D topography data is also known as a Planar Image. An n-by-m planar image I shall be represented as a function of two coordinates where at each point (xi, yj) (where i=1,...,n; j=1,...,m) there is a measured surface color or intensity denoted I(xi, yj). An example of 2D topographic data is an image taken through a comparison microscope; where each point I (xi, yj) is the RGB (red, green, blue) color value measured at the specified (xi, yj) position. The measured color or intensity is a function of the surface geometry and the environmental conditions (e.g., light position). Although reference scales may be included in the collected image, the points (xi, yj) may or may not be measured in standard units (e.g., micrometers).
3D topography data is also known as a Heightmap. An n-by-m heightmap H shall be represented asa function of two coordinates where at each point (xi, yj) (where i=1,...,n; j=1,...,m) there is ameasured surface height zi,j = H(xi, yj). All three coordinates xi, yj, and zi,j are measured in standardunits (e.g., micrometers). The surface H is a 1-to-1 representation of the actual object. An exampleof 3D topographic data is a primer surface measured using a confocal microscope; where each pointH(xi, yj) represents the surface height (in micrometers) measured at the specified (xi, yj) position. 3Ddata captured on hardware compliant with ANSI/ASB Standard 061, Firearm and Toolmarks 3DMeasurement Systems and Measurement Quality Control can be used in virtual comparisonmicroscopy.