Forensic Terms


A substance that is used to create and sometimes direct the spread of a fire. The most commonly used liquid accelerants include gasoline, lighter fluid, kerosene, and turpentine. See Gas Chromatography for information on how accelerants are identified.

Accident Reconstruction

The use of physical evidence to build a theoretical model of a given crime or accident scene.


A waxy, soap-like substance formed during the decomposition of bodies buried in moist places. It consists principally of insoluble salts of fatty acids. Also called “grave wax.” Composed of oleic, palmitic, and stearic acids.


Any of several alternative forms of a gene located at the same point on a particular pair of chromosomes. For example, the genes determining blood types A and B are alleles.


The science of the origin, culture, and development of humans. This can come into play when identifying skeletal remains, certain foodstuffs or items of clothing.


A protein that destroys or inactivates a specific antigen. Antibodies are found in the blood serum.


A substance, usually a protein, that stimulates the body to produce antibodies against it.


The crime of intentionally setting fire to buildings and other property.


The absence of sperm. Sterility in males.


The internal examination of a body after death; performed to confirm or determine the cause of death.


Common term for “Autoradiograph,” the final product in a DNA analysis. Autorads, which look very much like bar-codes, are formed by the reaction of electricity with genetic material (DNA). This reaction is unique to each sample of genetic material, providing an invaluable tool for identification. The reaction takes place on a nylon membrane which is photographed against x-ray film.


The science of the motion of projectiles. When a bullet is fired, it will have distinctive characteristics caused by the gun from which it is fired. Examiners can use this evidence to match bullets or bullet fragments to specific weapons.

Blood Spatter

The impact of spilled blood on surfaces. The pattern of the impact can provide vital information about the source of the blood. Blood spatter can help determine the size and type of wounds, the direction and speed with which the perpetrator or victim was moving, and the type of weapons used to create the blood spill.

Blood Volume Test

A test designed to show the quantity of blood shed in a particular area. Also designed to show how much blood was shed to create a given stain or blood spatter pattern, and the amount of time needed to create that stain.

Bloodstain Interpretation

The interpretation of size, shape, orientation, and distribution of bloodstains on various surfaces, and what information can be derived from the proper interpretation of the stains.


The scientific study of plants. Plant matter found at crime scenes is organic material and, like bodily fluids, has unique DNA sequences.

Bullet Track

The path of a bullet or projectile as it passes through matter, such as a body or a wall.


The diameter of the bore of a rifled firearm, usually expressed in hundredths of an inch.

Cast-off Blood

Blood that travels from a source due to the movement of that source. A bleeding person will cast-off blood, as will a weapon or other item that is in movement.

Cast-off Trails

The patterns that are created by cast-off blood.


A substance that accelerates the rates of chemical reactions but is not itself permanently changed by the reaction.

Cause of Death

Any injury or disease that results in physical trauma to the body, leading to death. Medical Examiners and/or Coroners will make the determination of cause, either at the scene or during a subsequent autopsy.

Centers for Disease Control (CDC)

Atlanta-based US government institution whose mission is to study and prevent disease in human and animal populations.


A rod-like structure in the nucleus of a cell along which genes are located.

Clinical Forensic Nursing

The application of clinical nursing practice to trauma survivors or to crime victims, involving the identification of the unrecognized, unidentified injuries, and the proper processing of forensic evidence

Composite Drawing

A sketch of a suspect produced from eyewitness-descriptions of one or more persons.

Computer Forensics

The application of computer technology for the purpose of examining potential evidence, including, but not limited to: theft of trade secrets; theft of, or destruction of property; and fraud. Specialists can recover data that has been deleted, encrypted, or damaged.

Crime Scene Staging

The attempt by a perpetrator or accomplice to alter a crime scene in order to reduce its evidentiary value.

Criminal Profiling

A tool used to aid investigators by providing information about the type of individual committing a specific crime. Information taken from the crime scene is integrated with known psychological theory and the history and background of the victim to draw up a biographical sketch of the perpetrator.


The study of criminal activity and how it is dealt with by the law.


A microscopic, single-cell form of marine or fresh-water algae, having siliceous cell walls. A body of water may contain many specifies of diatoms, but not all species of diatoms live in every body of water. Through painstaking examination, forensic scientists are able to identify the body of water wherein a given specifies of diatom lives.


Deoxyribonucleic Acid. Constructed of a double helix, DNA is the genetic material contained in cells. All organic matter has a specific DNA sequence; these sequences act like a genetic fingerprint and are currently the best method for identifying organic evidence like blood and other bodily fluids.

DNA Databanks

Databases which store DNA profiles collected from various classes of offenders. DNA from a given crime can be entered into the databank; it can then be matched with DNA profiles from other crimes, providing potential matches from previous convictions.

DNA Profiling

The process of testing to identify DNA patterns or types. In forensic science this testing is used to indicate parentage or to exclude or include individuals as possible sources of bodily fluid stains (blood, saliva, semen) and other biological evidence (bones, hair, teeth.)


A technique by which DNA fragments are placed in a gel and charged with electricity. The process separates the fragments by size, as part of the process of creating a genetic profile.

Endothermic Reaction

A chemical transformation in which heat energy is absorbed from the surroundings.


The scientific study of insects. The type of insects and their state of development, in combination with weather data and the condition of a decomposing body, can provide forensic investigators with accurate indicators of time of death.


The study of the occurrence, distribution, and causes of disease in human and animal populations.


A group of neurological disorders characterized by recurrent episodes of convulsive seizures, sensory disturbances, abnormal behavior, loss of consciousness, or all of these.


Anything that has been used, left, removed, altered, or contaminated during the commission of a crime.


The unique patterns created by skin ridges found on the palm sides of fingers and thumbs.


When a substance emits visible light when exposed to light of a shorter wavelength. Ultraviolet light, for example, will cause many objects to fluoresce.

Forensic Animation

The use of video technology to recreate crime scenes. Forensic animations are sometimes entered into evidence so jurors can view a sequence of events that otherwise could only be described by opposing attorneys. Some courts will not admit forensic animation into trial..

Forensic Linguistics

The forensic analysis of language such as letters, confessions, threats, and recorded speech.

Forensic Linguistics Demographics

The analysis of language to reveal traits of the speaker or writer such as possible geographic origin, education level, or occupation.

Forensic Meteorology

The study of weather patterns and how they relate to the investigation of crimes.

Forensic Psychologist

A trained mental health professional who examines suspects, perpetrators and victims in order to establish their psychological state and their ability to participate in the legal process.

Forensic Pathology

The study of how and why people die; a sub-specialty of pathology.

Forensic Science

The application of science to law and the investigation of criminal activity.

Forensic Sculpting

The attempt by a sculptor to create a likeness of a given individual using his or her skull.


A unit of inheritance located on a chromosome.

Genetic Fingerprinting

See DNA. The use of DNA technology to identify given individuals.

Geographic Profiling

A method to help investigators locate serial offenders. The sites and times of serial crimes in a given jurisdiction are entered into a computer program. This program then processes the information to give investigators a hypothetical area in which the perpetrator lives and operates.

Gas Chromatograph (GC)

A forensic tool used to identify the chemical makeup of substances used in the commission of crimes. The questioned substance is burned at high temperatures. The temperature at which this material becomes gas is then charted to determine its makeup.


A red blood cell protein responsible for transporting oxygen in the bloodstream. Also provides the red coloring of blood.

High Explosive

Any explosive with a velocity of detonation greater than 1000 meters per second. Dynamite is a high explosive.


The variety of a language unique to an individual.

Inorganic Compound

A chemical compound not based on carbon.


Stands for Light Amplification by Stimulated Emission of Radiation. A device that produces a coherent beam of optical radiation by stimulating electronic, ionic, or molecular transitions in order to create energy.

Latent Fingerprint

A fingerprint made by deposits of oils and/or perspiration, not usually visible to the human eye. Various technologies, including lasers, can be used to identify latent prints.

Lie Detector

Also known as a “Polygraph.” A machine that charts how respiration and other bodily functions change as questions are asked of the person being tested. An attempt to knowingly provide false answers can cause changes in bodily functions. Lie detector tests are not admissible in court.


The study of fresh waters (lakes and ponds — both natural and manmade) is including their biological, physical, and chemical aspects.


Also known as “liver mortis.” Postmortem discoloration caused by the gravitation of blood to various parts of the body. Can be used to help determine time of death, and placement of a body after death.

Low Explosive

An explosive with a velocity of detonation less than 100 meters per second. Gunpowder is a low explosive.


A chemical that is capable of detecting bloodstains diluted up to 10,000 times. Luminol is used to identify blood that has been removed from a given area. It is an invaluable tool for investigators at altered crime scenes.

M.O., or ‘Method of Operation’

From the Latin, Modus Operandi. Refers to method by which crimes are committed. Most often used on an individual basis to establish the pattern with which a perpetrator carries out a crime or series of crimes.

Manner of Death

An explanation of the way in which death is caused. Medicolegal manners of death are: homicide, suicide, accidental, natural, and undetermined.

Medical Examiner

A medical doctor who determines causes of death, performs autopsies, and acts as an expert witness in criminal and civil trials where cause and/or manner of death are relevant.

Micro-spectro Photometry

The use of an electronic microscope in which electrons are beamed onto the specimen. The analyst then charts the electron emissions that are created in order to identify the specimen.

Mitochondrial DNA (mtDNA)

A short sequence found outside of the cell nucleus in cells. Called mitochondria, this material is used in the absence of quality genetic material like blood, semen or saliva. It is passed only from mother to child; siblings share maternal mitochondria. Hairs and fingernails are good sources of mitochondria.

Monochromatic Light

Light having a single wavelength or frequency.


Analgesic or pain-killing substance that depresses vital body functions such as blood pressure, pulse rate, and breathing rate.


The study of the anatomy, growth, and diseases of the teeth. In the absence of other factors, ondontolgy can be used to identify human remains.

Orthotolidine Solution

A chemical solution that will determine whether a given stain contains blood.

Ouchterlony Test

A test that determines if a blood stain is human or animal.


The study of pollens.


The study of the essential nature of diseases and especially of the structural and functional changes produced by them.

Perspective Analysis

In order to determine the size of objects within a given photograph, analysts will identify one item in that photograph and measure the distance between that item and the camera used to make the photograph. This perspective allows them to measure everything in the photograph.

Petechial Hemorrhage

Small, pin-like hemorrhages that occur beneath the skin. Usually observed on the lining of the inner surface of the eyelids. This is a common result of death by asphyxiation or strangulation.

Photograph Analyst

A specialist who breaks down photographic images to identify suspects and to measure items and people within those images.

Physical Evidence

Any object that can establish that a crime has been committed, or can provide a link between a crime and its victim, or between a crime and its perpetrator.

Point-by-Point Analysis

When comparing a known object to one that needs to be identified, analysts will break down photos of each into small quadrants, and compare the respective similarities within those quadrants.

Polymerase Chain Reaction (PCR)

Scientists often refer to PCR as “photocopying DNA,” since it allows them to rapidly replicate DNA molecules. The technique usually is employed when a given sample of DNA is too small for forensic testing.

Psychological Profile

A tool used to aid investigators by providing speculative information about a perpetrator’s psychological makeup. Information from crime scenes is integrated with psychological theory and then cross-referenced against similar crimes. The result is a hypothetical model of the suspect that can include age, occupation, appearance, and personal information ranging from sexual preferences to dietary habits.

Psychopathic Personality

A person whose behavior is largely amoral and asocial, and who is characterized by perverse or impulsive behavior, and a lack of remorse for the consequences of this behavior.

Puncture Wound

A wound that is neither an impact wound nor one caused by a projectile; a piercing of the body, usually by a handheld object.

Questioned Documents

Any object that contains handwritten or typewritten markings whose source or authenticity are not known, but which is still relevant to the outcome of a legal proceeding.

Rape Kit

Biological material collected from a rape victim after the fact, to obtain genetic material of the suspected perpetrator.

Restriction Fragment

Length Polymorphisms (RFLP)

Length differences associated with strands of DNA. These differences vary from person to person, thus providing a means to further identify DNA.

Reverse Paternity DNA

A method by which a person’s blood can be identified by comparing the DNA profiles of individuals believed to be that person’s parents. Individual DNA makeup is a combination of parental DNA. Siblings will share these patterns while retaining unique DNA markers.

Ridge Characteristics

Ridge endings, bifurcations, enclosures, and other ridge details, which must match in two fingerprints for their common origin to be established.


An individual who secrets his or her blood-type antigen(s) in bodily fluids. Before DNA technology, blood type from bodily fluids other than blood could only be obtained from secretors, who make up about 80 percent of the population.


A technology dealing with the properties and actions of serums in blood; also known as “blood analysis.” This was the preferred
method of typing blood before the advent of DNA.


The liquid that separates from the blood when a clot is formed.


A technology that measures how a given object responds to frequencies within the light spectrum. Objects can be identified and their properties visually clarified by use of this technology.


A physical change from a solid directly into a gaseous state.

Super Glue Fuming

Techniques used to develop latent fingerprints on non-porous surfaces. A chemical in the glue reacts with and adheres to the finger oils, and then expose latent prints.


The study of poisons and drugs and their effect on human and animal populations.

Trace Evidence

Material deposited at a crime scene that can only be detected through a deliberate processing procedure. An individual enteringany environment will deposit traces of his or her presence, and this material can be used as evidence. Common sources of traceevidence are hairs and fibers.