TSA Forensic Science 2024 Nats Studying

Archive Copy

A copy of data placed on media suitable for long-term storage, from which subsequent working copies can be produced.

Artifact

A visual/aural aberration in an image, video or audio recording resulting from a technical or operational limitation. Examples include speckles in a scanned picture or “blocking” in images compressed using the JPEG standard.

Capture

The process of recording data, such as an image, video sequence or audio stream.

Compression

The process of reducing the size of a data file. (See also, “Lossy Compression” and “Lossless Compression”.)

De-interlacing

Separating an interlaced frame into two discrete fields.

Field

An element of a video signal containing alternate horizontal lines. For interlaced video, the scanning pattern is divided into two sets of spaced lines (odd and even) that are displayed sequentially. Each set of lines is called a field, and the interlaced set of the two sets of lines is a frame.

Frame

Lines of spatial information of a video signal. For interlaced video, a frame consists of two fields, one of odd lines and one of even lines, displayed in sequence. For progressive scan (non-interlaced) video, the frame is written through successive lines that start at the top left of the picture and finish at the bottom right.

Image Analysis

A sub-discipline of Digital & Multimedia Evidence, which involves the application of image science and domain expertise to examine and interpret the content of an image and/or the image itself in legal matters.

Image Comparison

The process of comparing images of questioned objects or persons to known objects or persons or images thereof, and making an assessment of the correspondence between features in these images for rendering an opinion regarding identification or elimination.

Image Content Analysis

The drawing of conclusions about an image. Targets for content analysis include, but are not limited to: the subjects/objects within an image; the conditions under which, or the process by which, the image was captured or created; the physical aspects of the scene (e.g., lighting or composition); and/or the provenance of the image.

Interlaced scan

A technique of combining two television fields in order to produce a full frame. The two fields are composed of only odd and only even lines, which are displayed one after the other but with the physical position of all the lines interleaving each other, hence interlace³.

Interpolation

A method of image processing whereby one pixel, block, or frame is displayed or stored based on the differences between the previous and subsequent pixel, block or frame of information. [Taken from the Encyclopedia of Photography 3rd Edition] This is often done to increase the apparent clarity of an image.

Multiplexer/Demultiplexer

A device used to combine multiple video signals into a single signal or separate a combined signal. These devices are frequently used in security and law enforcement applications for recording and/or displaying multiple camera images simultaneously or in succession.

Nominal resolution

The numerical value of pixels per inch as opposed to the achievable resolution of the imaging device. In the case of flatbed scanners, it is based on the resolution setting in the software controlling the scanner. In the case of digital cameras, this refers to the number of pixels of the camera sensor divided by the corresponding vertical and horizontal dimension of the area photographed.

Sharpening

A process used to emphasize edge detail in an image by enhancing the high frequency components.

Time lapse video recording

Process by which images are recorded at less than the standard rate of frames per second (NTSC–29.97; PAL–25.00) thus extending the period of time that can be covered by the storage medium.

Video stabilization

The process of positioning individual frames so that a selected object or person will remain in the same location as the video is played.

Work copy

A copy or duplicate of a recording or data that can be used for subsequent processing and/or analysis.

Angle of Impact

the angle at which a blood drop strikes a surface

Area of Convergence

The area containing the intersections generated by lines drawn through the long axes of individual stains that indicates in two dimensions the location of the blood source.

Area of origin

The three-dimensional location from which blood spatter originated.

Backspatter Pattern

A bloodstain pattern resulting from blood drops that traveled in the opposite direction of the external force applied; associated with an entrance wound created by a projectile.

Blood clot

A gelatinous mass formed by a complex mechanism involving red blood cells, fibrinogen, platelets, and other clotting factors.

Bloodstain

A deposit of blood on a surface.

Bloodstain Pattern

A grouping or distribution of bloodstains that indicates through regular or repetitive form, order, or arrangement the manner in which the pattern was deposited.

Bubble ring

An outline within a bloodstain resulting from air in the blood.

Cast-off Pattern

A bloodstain pattern resulting from blood drops released from an object due to its motion.

Cessation Cast-off Pattern

A bloodstain pattern resulting from blood drops released from an object due to its rapid deceleration.

Drip Pattern

A bloodstain pattern resulting from a liquid that dripped into another liquid, at least one of which was blood.

Drip Stain

A bloodstain resulting from a falling drop that formed due to gravity.

Drip Trail

A bloodstain pattern resulting from the movement of a source of drip stains between two points.

Edge Characteristic

A physical feature of the periphery of a bloodstain.

Expiration Pattern

A bloodstain pattern resulting from blood forced by airflow out of the nose, mouth, or a wound.

Flow Pattern

A bloodstain pattern resulting from the movement of a volume of blood on a surface due to gravity or movement of the target.

Forward Spatter Pattern

A bloodstain pattern resulting from blood drops that traveled in the same direction as the impact force.

Impact Pattern

A bloodstain pattern resulting from an object striking liquid blood.

Luminol

(C₈H₇N₃O₂) - is a versatile chemical that exhibits chemiluminescence, with a striking blue glow, when mixed with an appropriate oxidizing agent. Luminol is used by forensic investigators to detect trace amounts of blood left at crime scenes as it reacts with iron found in hemoglobin.

Mist Pattern

A bloodstain pattern resulting from blood reduced to a spray of micro-drops as a result of the force applied.

Parent Stain

A bloodstain from which a satellite stain originated.

Perimeter Stain

An altered stain that consists of the peripheral characteristics of the original stain.

Plasma

The clear, yellowish fluid portion of blood.

Platelet

An irregularly shaped cell-like particle in the blood that is an important part of blood clotting. Platelets are activated when an injury causes a blood vessel to break. They change shape from round to spiny, “sticking” to the broken vessel wall and to each other to begin the clotting process.

Pool

A bloodstain resulting from an accumulation of liquid blood on a surface.

Projected Pattern

A bloodstain pattern resulting from the ejection of a volume of blood under pressure, such as a spurt or spray.

Satellite Stain

A smaller bloodstain that originated during the formation of the parent stain as a result of blood impacting a surface.

Saturation Stain

A bloodstain resulting from the accumulation of liquid blood in an absorbent material.

Serum Stain

The stain resulting from the liquid portion of blood (serum) that separates during coagulation.

Spatter Stain

A bloodstain resulting from a blood drop dispersed through the air due to an external force applied to a source of liquid blood.

Spines

A bloodstain feature resembling spokes or rays emanating out from the edge of a blood drop; they result from the drop contacting a non-smooth surface.

Splash Pattern

A bloodstain pattern resulting from a volume of liquid blood that falls or spills onto a surface.

Swipe Pattern

A bloodstain pattern resulting from the transfer of blood from a blood-bearing surface onto another surface, with characteristics that indicate relative motion between the two surfaces.

Transfer Stain

A bloodstain resulting from contact between a blood-bearing surface and another surface.

Void

An absence of blood in an otherwise continuous bloodstain or bloodstain pattern.

Wipe Pattern

An altered bloodstain pattern resulting from an object moving through a preexisting wet bloodstain.

Alternate light source

Special lighting device that produces visible and invisible light at various wavelengths to help investigators locate and visually enhance items of evidence (e.g., fluids, fingerprints, clothing fibers).

Associative evidence

any evidence that can link a person or an item to the scene of the crime.

Biological evidence

physical evidence such as bodily fluids that originated from a human, plant or animal.

Chain of custody

The process used to maintain and document the chronological history of the evidence. Documents record the individual who collects the evidence and each person or agency that subsequently takes custody of it. This chain of custody verifies that the evidence being analyzed is the same evidence found at the scene and helps ensure there was no opportunity for the evidence to be tampered with.

Contamination

The unwanted transfer of material from another source to a piece of physical evidence. The inadvertent touching of a weapon, thereby adding fingerprints to it is an example of evidence contamination.

Control sample

material of a known source that presumably was uncontaminated during the commission of the crime.

Cross-contamination

The unwanted transfer of material between two or more sources of physical evidence. For example, improperly collecting biological evidence such as blood could lead to one sample mixing with another sample and contaminating both.

Elimination sample

material of a known source taken from a person who had lawful access to the scene.

First responders

The initial responding law enforcement officer(s) and/or other public safety official(s) or service provider(s) arriving at the scene prior to the arrival of the investigator(s) in charge.

Fluorescent powders

Powder containing fluorescent chemicals that is applied to a surface to reveal latent prints; used in conjunction with an alternate light source.

Impression evidence

Objects or materials that have retained the characteristics of other objects that have been physically pressed against them.

Latent print

A fingerprint, palm print or footprint that is not readily visible under normal lighting.

Locard’s Exchange Principle

the theory that every person who enters or exits an area will deposit or remove physical material from the scene.

Other responders

Individuals who are involved in an aspect of the crime scene, such as perimeter security, traffic control, media management, scene processing, and technical support, as well as prosecutors, medical personnel, medical examiners, coroners, forensic examiners, evidence technicians, and fire and rescue officers.

Presumptive Test

a test that is typically conducted at a crime scene that provides investigators with basic information regarding the compound in question. Presumptive tests can typically reveal the class of evidence, but are unable to confirm the specific compounds of which it is comprised.

Probative

possessing the potential to provide details that are valuable to an investigation.

Reconstructive evidence

reconstructive evidence allows investigators to gain an understanding of the actions that took place at the scene; a broken window, a blood spatter pattern, bullet paths and shoe prints.

Reference sample

material from a verifiable/documented source which, when compared with evidence of an unknown source, shows an association or linkage between an offender, crime scene, and/or victim.

Trace evidence

Physical evidence that results from the transfer of small quantities of materials (e.g., hair, textile fibers, paint chips, glass fragments, gunshot residue particles).

Transient evidence

Evidence which by its very nature or the conditions at the scene will lose its evidentiary value if not preserved and protected (e.g., blood in the rain).

Unknown/questioned sample

evidence of unknown origin; these samples could be found at a crime scene, transferred to an offender during commission of a crime, or recovered from more than one crime scene.

Cloud Computing

software, applications and digital storage that is accessed on the Internet through a web browser or desktop or mobile app. The software and user’s data are stored on servers at a remote location.

Data

Information in analog or digital form that can be transmitted or processed.

Data Extraction

A process that identifies and recovers information that may not be immediately apparent.

Encryption

A procedure that converts plain text into symbols to prevent anyone but the intended recipient from understanding the message.

File Format

The structure by which data is organized in a file.

Forensic Wipe

A verifiable procedure for sanitizing a defined area of digital media by overwriting each byte with a known value; this process prevents cross-contamination of data.

Handheld (Mobile) Devices

Handheld devices are portable data storage devices that provide communications, digital photography, navigation systems, entertainment, data storage, and personal information management.

Hash or Hash Value

Numerical values that represent a string of text (search term), generated by hashing functions (algorithms). Hash values are used to query large sums of data such as databases or hard drives for specific terms. In forensics, hash values are also used to substantiate the integrity of digital evidence and/or for inclusion and exclusion comparisons against known value sets.

Log File

A record of actions, events, and related data.

Media

Objects on which data can be stored. Includes hard drives, thumb drives, CD/DVD, floppy discs, SIM cards from mobile devices, memory cards for cameras, etc.

Metadata

Data, frequently embedded within a file, that describes a file or directory, which can include the locations where the content is stored, dates and times, application specific information, and permissions. Examples: Email headers and website source code contain metadata.

Partition

User defined section of electronic media. Partitions can be used to separate and hide information on a hard drive.

Source Code

The instructions written in a programming language used to build a computer program.

Work Copy

A copy or duplicate of a recording or data that can be used for subsequent processing and/or analysis. Also called an image.

Write Block/Write Protect

Hardware and/or software methods of preventing modification of content on a media storage unit like a CD or thumb drive.

Allele

The characteristics of a single copy of a specific gene, or of a single copy of a specific location on a chromosome.

Autosomal DNA

DNA found in chromosomes which are not sex chromosomes.

Chromosome

The biological structure by which hereditary information is physically transmitted from one generation to the next; located in the cell nucleus, it consists of a tightly coiled thread of DNA with associated proteins and RNA; the genes are arranged in linear order along the DNA.

Combined DNA Index System (CODIS)

The generic term used to describe the FBI’s program of support for criminal justice DNA databases as well as the software used to run National DNA Index System (NDIS) databases; CODIS is made up of the National DNA Index System (NDIS), the State DNA Index System (SDIS) and Local DNA Index Systems (LDIS).

DNA (Deoxyribonucleic acid)

Often referred to as the “blueprint of life;” genetic material present in the nucleus of cells which is inherited from each biological parent that determines each person’s individual characteristics. An individual’s DNA is unique except in cases of identical twins.

DNA Profiling

The result of determining the relative positions of DNA sequences at several locations on the molecule; each person (except identical twins) has a unique DNA profile when used in the context of the CODIS database, which evaluates 13 specific DNA locations.

DNA Fingerprinting

Analyses of the lengths of the fragments reveal that when looking at multiple VNTRs (variable number of tandem repeats) within and between individuals, no two people have the same assortment of lengths, except identical twins; this technique became known to the public as “DNA fingerprinting” because of its powerful ability to discriminate between unrelated individuals.

Epithelial cells

Cells that cover the inner and outer linings of body cavities.

Forensic DNA Analysis

The process of identifying and evaluating biological evidence in criminal matters using DNA technologies.

Genotype

The genetic constitution of an organism, as distinguished from its physical appearance (its phenotype); the designation of two alleles at a particular locus is a genotype.