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.
An approximation derived from a statistical sample of a population.
The estimated age interval expresses the mathematically determined minimum and maximum associated age range at a particular level of uncertainty.
Consists of the consideration of data observed in the comparison and the weight of the correspondence and/or non-correspondence between two items, unknown and known.
The weighting of the aggregate strength of the evidence (observed similarities and dissimilarities when considering two competing propositions) between the observed data in the friction ridge impressions being compared in order to formulate a source conclusion.
The weighting of the aggregate strength of the evidence (observed similarities and dissimilarities when considering two competing propositions) between the observed data in the friction ridge impressions being compared in order to formulate a source conclusion.
The weighting of the aggregate strength of the evidence (observed similarities and dissimilarities when considering two competing propositions) between the observed data in the friction ridge impressions being compared in order to formulate a source conclusion.
An individual with relevant training and experience in the discipline being evaluated, who assesses the performance of canine, canine handler, or canine team while showing no bias or partiality. (See certifying official/assessor.)
the change of a substance from the liquid phase to the gaseous or vapor phase, which can occur at or below the normal boiling point of the liquid.
the change of a substance from the liquid phase to the gaseous or vapor phase, which can occur at or below the normal boiling point of the liquid.
A body of facts, information, or material objects indicating whether a belief or proposition is true or valid.
A body of facts, information, or material objects indicating whether a theory or proposition is true or valid.
A body of facts, information, or material objects indicating whether a theory or proposition is true or valid.
A body of facts, information, or material objects indicating whether a belief or proposition is true or valid.
The process of a canine locating and indicating items that contain a trained odor/human scent. This may be non-specific or targeted based on the discipline. (See article search.)
The process of a canine locating and indicating items that contain a trained human scent. This may be non-targeted or targeted based on the discipline.
A canine trained to locate and indicate items in question by means of detecting a trained odor/ human scent.
Data derived from biological specimens of unknown source.
Data generated from an evidentiary sample and not from a reference sample.
Biological sample recovered from a crime scene or collected from persons or objects associated with a crime.
A photograph that contains sufficient quality of information for the purpose of conducting aforensic footwear and tire examination.
in facial identification, an individual whose role it is to perform a facial examination.
An individual authorized to conduct independent friction ridge examinations for the forensic service provider by observing and interpreting data, making decisions, forming conclusions and opinions, issuing reports and/or providing testimony. Use of the term “examiner” in this document refers to a “competent friction ridge examiner” and not a “trainee.”
An individual authorized to conduct independent friction ridge examinations for the forensic service provider by observing and interpreting data, making decisions, forming conclusions and opinions, issuing reports and/or providing testimony. Use of the term “examiner” in these documents refers to a “competent friction ridge examiner” and not a “trainee.”
An individual who has successfully completed their FSP’s training program, and is authorized to conduct independent friction ridge examinations for the FSP by observing and interpreting data, making decisions, forming conclusions and opinions, issuing reports and/or providing testimony. Use of the term “examiner” in these documents refers to a “friction ridge examiner” and not a “trainee,” refer to those definitions for further clarification.
An individual who has successfully completed their FSP’s training program, and is authorized to conduct independent friction ridge examinations for the FSP by observing and interpreting data, making decisions, forming conclusions and opinions, issuing reports and/or providing testimony. Use of the term “examiner” in these documents refers to a “friction ridge examiner” and not a “trainee.” Refer to those definitions for further clarification.
An individual authorized to conduct independent friction ridge examinations for the forensic service provider by observing and interpreting data, making decisions, forming conclusions and opinions, issuing reports and/or providing testimony. Use of the term “examiner” in these documents refers to a “competent friction ridge examiner” and not a “trainee.”
Although NIEM contains thousands of elements it does not contain everything needed inan XML exchange. It contains the most common building blocks. In addition,implementers can define, in other exchange schemas, user-defined elements from theimplementers domain.
a filter used in fluorescence microscopy that transmits specific bands or wavelengths of energy capable of inducing visible fluorescence in various substrates.
A result that compared items did not originate from the same source, are not the same substance, or do not share the same composition or classification, based on an exclusionary difference.
Also referenced in ASB 097, Terminology Used for Forensic Footwear and Tire Evidence.
A type of location search in which a scent match is not indicated by the canine thereby excluding an individual as the scent contributor.
the result of a comparison between two hair samples in which the characteristics of the questioned hair differ from those present in the known hair sample, and therefore the donor of the known sample cannot be included as a possible source of the questioned hair.
Discussion—This result is reached in a comparative hair examination when differences are noted in the macroscopic or microscopic characteristics between the questioned and known hairs; however, the differences are insufficient for an absolute exclusion of a person as a possible source. This could be due to the natural variation that occurs in hairs as a biological specimen, the effect that time or environment can have upon a hair, or the reference sample does not capture the complete variation of the individual's hair.
A conclusion that eliminates an individual as a contributor of DNA obtained from an evidentiary sample based on the comparison of DNA data.
the result of a comparison between two hair samples in which exclusionary differences are observed in the characteristics of the questioned hair that are not present in the known hair sample, and therefore the donor of the known sample can be excluded as a possible source of the questioned hair.
Discussion—This result is reached in a comparative hair examination when exclusionary differences (for example, color, characteristics indicative of ancestry) are noted in the macroscopic or microscopic characteristics between the questioned and known hairs. In these circumstances, the source of the known hairs, as represented by the known sample, is eliminated as a possible source of the questioned hair.
a difference in one or more characteristics between compared items that is sufficient to determine that the compared items did not originate from the same source, are not the same source, or do not share the same composition or classification.
Also referenced in ANSI/ASTM E2228-23a Standard Guide for Microscopical Examination of Textile Fibers, ANSI/ASTM E2227-23e1 Standard Guide for Forensic Examination of Dyes in Textile Fibers by Thin-Layer Chromatography, ANSI/ASTM E2225-23 Standard Guide for Forensic Examination of Fabrics and Cordage, ANSI/ASTM E3295-23 Standard Guide for Using Micro X-Ray Fluorescence (μ-XRF) in Forensic Polymer Examinations, ANSI/ASTM E3316-22 Standard Guide for Forensic Examination of Hair by Microscopy, ANSI/ASTM E3296-22 Standard Guide for Using Pyrolysis Gas Chromatography and Pyrolysis Gas Chromatography-Mass Spectrometry in Forensic Polymer Examinations, ANSI/ASTM E3260-21 Standard Guide for Forensic Examination and Comparison of Pressure Sensitive Tape, ANSI/ASTM E1732-24e1 Standard Terminology Relating to Forensic Science.
Evidence that may be favorable to the accused, impeach the prosecution’s evidence, or mitigate the offense.
The friction ridge prints of an individual, associated with a known or claimed identity,and deliberately recorded electronically, by ink, or by another medium (also called 'known prints').
a specimen of physical evidence of known origin.
The deliberately recorded images or impressions from the friction ridge skin of an individual. NOTE Examples may include, but are not limited to, inked tenprints, inked palm prints, Livescan prints, powder and lift prints, casted/moulded prints, or photographs of friction ridge skin.
The deliberately recorded images or impressions from the friction ridge skin of an individual.
NOTE Examples may include, but are not limited to, inked tenprints, inked palm prints, Livescan prints, powder and lift prints, casted/moulded prints, or photographs of friction ridge skin.
The deliberately recorded images or impressions from the friction ridge skin of an individual. NOTE Examples may include, but are not limited to, inked tenprints, inked palm prints, Livescan prints, powder and lift prints, casted/moulded prints, or photographs of friction ridge skin.
The deliberate recorded images or impressions from the friction ridge skin of an individual.
Circumstances that would cause a reasonable person to believe that relevant prompt action was necessary to prevent physical harm to persons or animals, the destruction of relevant evidence or some other consequence improperly frustrating legitimate law enforcement efforts.
Quantity defining an interval about a result of a measurement that may be expected to encompass a large fraction of the distribution of values that could reasonably be attributed to the measurand. DISCUSSION(1) The fraction may be regarded as the coverage probability or level of confidence of the interval. (2) To associate a specific level of confidence with the interval defined by the expanded uncertainty requires explicit or implicit assumptions regarding the probability distribution characterized by the measurement result and its combined standard uncertainty. The level of confidence that may be attributed to this interval can be known only to the extent to which such assumptions can be justified. (3) An expanded uncertainty U is calculated from a combined standard uncertainty uc and coverage factor k using: U =k X uc.
quantity defining an interval about a result of a measurement that may be expected to encompass a large fraction of the distribution of values that could reasonably be attributed to the measurand.
Discussion—(1) The fraction may be regarded as the coverage probability or level of confidence of the interval.
(2) To associate a specific level of confidence with the interval defined by the expanded uncertainty requires explicit or implicit assumptions regarding the probability distribution characterized by the measurement result and its combined standard uncertainty. The level of confidence that may be attributed to this interval can be known only to the extent to which such assumptions can be justified.
(3) An expanded uncertainty, U, is calculated from a combined standard uncertainty, uc, and coverage factor, k, using: U=k×uc.
The number of distinct alignments expected by chance; the default sorting metric in BLAST search results.
Anyone testing any idea has a strong expectation that leads to an influence about the outcome.
A person displaying special skill and knowledge in a given area derived from training, education, or experience.