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 normal frequency of occurrence of a specified response per unit of time for that individual canine or group of canines.
The a) BLAST algorithm, and b) a suite of database search programs that implement variations of this algorithm to generate alignments between a nucleotide or protein sequence in a query, and nucleotide or protein sequences within a database.
A set of standards, controls, and/or case samples that are contemporaneously prepared, extracted, and analyzed in a particular sequence
in facial identification, a mode of searching records in an automated system in which a group of probes are simultaneously or sequentially launched.
See batch mode search
The FBI's Biometric Center of Excellence.
Biometric Data Block used in CBEFF.
A rounded mass of resolidified metal on the end of the remains of an electrical conductor or conductors that was caused by arcing and is characterized by a sharp line of demarcation between the melted and unmelted conductor surfaces.
current that impinges on the specimen.
Note—Also referred to as probe current.
the bright halo near the boundary of a fiber that moves with respect to that boundary as the microscope is focused through best focus when the fiber is mounted in a medium that differs from its refractive index.
a method for determining the refractive index of a fiber relative to its mountant by noting the direction in which the Becke line moves when the focus is changed.
Discussion—The Becke line always moves toward the higher refractive index medium (fiber or mountant) when focus is raised (stage is lowered) and towards the lower refractive index medium when focus is lowered (stage is raised). At the point where the index of the fiber matches the index of the mounting medium, the Becke line is no longer visible. The Becke line is generally viewed at a wavelength of 589 nm (the D line of Sodium [nD]).
Any measurable, physical response of a canine. Can be voluntary (goal directed) or involuntary (reflexive).
A series of independent behaviors that are linked together.
The application of a behavioral technique (e.g., positive reinforcement) to change a behavior.
A trial where the judge sits as the trier of fact.
primer/case system, designed by Col. Hiram Berdan, having two or more flash holes consisting of a cup, explosive mixture, and covering foil or paper; the anvil is an integral part of the cartridge case head in the bottom of the primer pocket.
A system of processes, checks and testing that may deliver an outcome that has fewer problems and fewer unforeseen complications, and that may combine the attributes of the most efficient and most effective ways of accomplishing a task based on proven and provable methods, while maintaining overall operational integrity and remaining within the bounds of legally accepted practices.
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
An 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
Preconception; prejudice; taint; partiality. Since most persons have biases, the issue is whether the bias is such that impartiality cannot be achieved and a fair outcome cannot occur. Any predisposition that a judge or arbitrator may have may be grounds for recusal. Any predisposition that a witness may have may be grounds for impeachment by cross-examination. Any predisposition that a juror may have may be grounds for excusal determined by through a process known as voir dire. This use of the term 'bias' is not that as used in statistical evaluations. (See cognitive bias, contextual bias, and experimental bias.)
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.
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
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.
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.
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 submission of a biometric reference as a probe against a biometric system for identification (one-to-many) or verification (one-to-one). (Compare attempt.)
material exhibiting birefringence.
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).
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.