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 variance of measured results as influenced by human perceptions or systemic factors. Note: It is beyond the scope of this document to outline the numerous types of biases
estimate of systematic measurement error, calculated as the difference between the mean of several measurements under identical conditions to a known “true” value. It is often reported as a percent difference.
Estimate of systematic measurement error, calculated as the difference between the mean of several measurements under identical conditions to a known “true” value
A tendency for an individual’s preexisting beliefs, expectations, motives, or the situational context to influence their sampling, observations, results, interpretations, or opinions, or their confidence in the aforementioned.
Also referenced in ANSI/ASB Standard 024 Standard for Training and Certification of Canine Detection of Humans: Location Check Using Pre‐scented Canines, ASB Technical Report 025 Crime Scene/Death Investigation – Dogs and Sensors – Terms and Definitions, ANSI/ASB Standard 024 Standard for Training and Certification of Canine Detection of Humans: Location Check Using Pre‐scented Canines, ANSI/ASB Standard 088 General Guidelines for Training, Certification, and Documentation of Canine Detection Disciplines, ANSI/ASB Standard 154 Standard for Training on Testimony for Forensic Biology
A tendency to search for, collect, perceive, or interpret information in a manner that supports preconceptions, expectations, or desires.
NOTE: This is a type of cognitive bias.
A tendency for exposure to or knowledge of case-specific information to affect the impartial collection, perception, or interpretation of evidence.
NOTE: This is a type of cognitive bias.
Also referenced in ASB Technical Report 025, Crime Scene/Death Investigation – Dogs and Sensors – Terms and Definitions
A systematic tendency for estimates or measurements to be above or below their true values.
NOTE 1: Statistical bias arises from systematic as opposed to random error.
NOTE 2: Statistical bias can occur in the absence of prejudice, partiality, or discriminatory intent.
an oriented polypropylene film in which the polymer has been stretched in both the machine direction and cross direction during the manufacturing process. Tapes with such films cannot be torn by hand.
Allele designations corresponding to the window of fragment sizes for each allele, determined by empirical testing
An allele designation corresponding to the window of fragments sizes for each allele, determined by empirical testing.
a high explosive consisting of a separate oxidizer and fuel that can be acquired, stored, or shipped individually, but when combined form an explosive mixture.
a non-volatile portion of a paint which serves to bind or cement the pigment particles together.
a nonvolatile portion of the liquid vehicle of a coating, which serves to bond or cement the pigment particles together.
in facial identification, (1) any technique used by a facial recognition (FR) system to organize or optimize searching based upon some piece(s) of metadata; (2) the process of parsing (examining) or classifying data to accelerate or improve biometric matching.
The age corresponding with the developmental, degenerative, biochemical or isotopic status of an individual. Note: The rate at which organ systems age may differ from the individual's chronologic age.
Any liquid biological specimen that is typically pipetted for analysis (e.g., blood, urine, bile, serum, vitreous humor, oral fluid)
The description of an individual’s estimated age, sex, ancestry, and living stature derived from an anthropological (skeletal) analysis.
The description of an individual’s estimated age, sex, ancestry, and living stature derived from an anthropological (skeletal) analysis.
The description of an individual’s estimated age, sex, population affinity, and stature derived from skeletal analysis.
The description of an individual’s estimated age, sex, ancestry/population affinity, and living stature derived from an anthropological (skeletal) analysis.
The description of an individual’s estimated sex, ancestry, age, and living stature derived from an anthropological (skeletal) analysis.
the submission of a biometric reference as a probe against a biometric system for identification (one-to-many) or verification (one-to-one). (Compare attempt.)
property of some crystals, those having more than one refraction index; this property will result in interference colors, which are viewed through a polarized light microscope.
property of some crystals, those having more than one refractive index; this will result in interference colors which are viewed through a polarized light microscope.
the numerical difference in refractive indices (n) for a fiber, given by the equation:
|n|| - n ? |
Birefringence (B) can be calculated by determining the retardation (r) and thickness (T) at a particular point in a fiber and by using the equation:
B = r (nm)⁄1000T (μm).
material exhibiting birefringence.
the number of bits (binary digits) used to specify the brightness or color range of each pixel in an image sensor.
a continuous stream of bits transmitted over a channel with no separators between the character groups.
in computer forensics, an exact, bit-for-bit reproduction of all data objects independent of any physical media upon which that data is stored. (Compare copy.)
a low explosive composed of potassium nitrate, sulfur, and charcoal; commercial products are generally glazed and produced in specific granulation size ranges.
Discussion—Sodium nitrate can be found in place of potassium nitrate.
A commercially produced low explosive powder which is designed to replace traditional black powder in muzzle loading weapons; formulations can include potassium perchlorate in addition to potassium nitrate, or can use other fuels such as ascorbic acid.
Discussion—Many black powder substitutes are sulfur-free.
broad, flat, elongated crystals.
Any area or container where target odor/scent is not present. (See blank search.)
a control where a specified component(s) is not present. Discussion - - Blanks with various designations can be specified, such as system blank, process blank, method blank, reagent blank, solvent blank, etc. Certain blanks may also serve as a negative control.
A biological fluid or tissue (or synthetic substitute) without target analyte or internal standard
A training or certification exercise in which the target odor/scent is not present.
A training or certification exercise in which the target scent is not present.
A training or certification exercise in which the target scent is not present.
A training or certification exercise in which the target scent is not present.
A known odor/scent sample that is used to assess the canine's proficiency in a non-matching odor/scent scenario. The canine is expected to give a negative response.
The expanding leading edge of an explosion reaction that separates a major difference in pressure between normal ambient pressure ahead of the front and potentially damaging high pressure at and behind the front.
a non-detonator sensitive explosive that must be initiated by a booster, or that requires a primer to detonate.
Discussion—Many ammonium nitrate-based explosives fall into this category.
a cylindrical shell, usually of metal, containing both a primary high explosive and a secondary high explosive, which is used to initiate other explosives; also known as a detonator or cap.
Small extraneous spot found near inked regions of checkwriter impressions that is characteristic of machines that use ribbons as their ink source.
Boiling liquid expanding vapor explosion.