Comprehensive Study Notes on Forensic Science Terminology and Methods

Forensic Science: The application of science to law and legal proceedings.
Criminology: The study of criminal activity and how it is dealt with by the legal system.
Evidence: Anything that has been used, left, removed, altered, or contaminated during the commission of a crime or other event under investigation.
Physical Evidence: Any tangible object that can help explain an event under investigation.
- Functions to establish that a crime has been committed.
- Provides a direct link between a crime and its victim, or between a crime and its perpetrator.
Trace Evidence: Material deposited at a crime or accident scene that can only be detected through a deliberate processing procedure.
- Concept: An individual entering an environment will deposit traces of their presence, which can be harvested and used as evidence.
- Common Types: Hairs and clothing fibers.
Point-by-Point Analysis: A comparative identification method where, when comparing a known object to an unidentified object, analysis breaks down photographs of each into small portions and compares the respective similarities within those specific portions.

Autopsy: The comprehensive internal and external examination of a body after death.
- Primary Purpose: Conducted to confirm or determine the precise cause of death.
- Pre-Death Condition Assessment: Used to establish conditions prior to death, including the specific type of food last consumed and the exact time it was consumed.

Ballistics: The study of the motion of bullets and their detailed examination for distinctive characteristics after being fired.
- Application: Forensic examiners analyze ballistics evidence to match fired bullets or bullet fragments to specific weapons.
Caliber: The diameter of the bore of a rifled firearm, typically expressed in hundredths of an inch or in millimeters.
- Example: A Colt 45 firearm has a bore diameter of $.45$ of an inch.
Bullet Track: The path of a bullet or projectile as it passes through matter, such as a human body or a wall.
Trajectory: The path followed by a projectile in motion.

Serology: A technology and scientific field dealing with the properties and actions of serums in blood; also known as "blood analysis".
Hemoglobin: A protein found within red blood cells responsible for transporting oxygen into the bloodstream. It also provides the characteristic red coloring of blood.
Blood Spatter: The specific pattern formed when blood strikes a surface.
- Diagnostic Capabilities: Yields vital information regarding the source of the blood, including the side and type of the wound, the direction and speed at which the perpetrator or victim was moving, and the type of weapon used to inflict the wound.
Bloodstain Interpretation: The evaluation and interpretation of the size, shape, orientation, and distribution of bloodstains across various surfaces to derive accurate information about the event sequence.
Luminol: A chemical reagent capable of detecting bloodstains diluted up to $10,000$ times.
- Purpose: Used to reveal blood that has been cleaned or removed from a given area, serving as an invaluable tool at altered crime scenes.

DNA (Deoxyribonucleic Acid): Double-helix strands containing the genetic code.
- Biological Distribution: In higher organisms, identical DNA exists in the nucleus of every cell and defines an individual's personal characteristics.
- Structure: Contains proportions of DNA that encode proteins common to a species, as well as distinct regions of "junk" DNA unique to each individual within that species.
- Forensic Application: Frequently found in blood and other bodily fluids, providing the single best method presently known for uniquely identifying a person or animal who left fluid traces at a scene.
Gene: A unit of inheritance consisting of a specific sequence of DNA that dictates a particular characteristic in an organism.
DNA Electrophoresis: A technique in which DNA fragments are placed inside a gel matrix and charged with electricity.
- Mechanism: An applied electric field separates the DNA fragments by size as part of the process of building a genetic profile.
DNA Profiling: The testing process used to identify specific DNA patterns or types.
- Applications: Used in forensic science to determine parentage or to include/exclude individuals as possible sources of bodily fluid stains (blood, saliva, semen) and other biological evidence (bones, hair, teeth).

Fingerprint: Unique patterns created by friction skin ridges located on the palm, sides of fingers, and thumbs.
Latent Fingerprint: A fingerprint formed by natural deposits of oils and/or perspiration that is typically invisible to the unassisted human eye.
- Detection: Identified using specialized technologies, including lasers.
Ridge Characteristics: Microscopic ridge details—including ridge endings, bifurcations, and enclosures—that must match between two fingerprints to establish a common origin.
Super Glue Fuming: A processing technique used to develop latent fingerprints on non-porous surfaces.
- Mechanism: A chemical component in cyanoacrylate glue reacts with and adheres to finger oils, exposing the unseen latent prints.

Catalyst: A chemical substance that accelerates the rate of a chemical reaction without undergoing any permanent chemical change itself.
Gas Chromatograph (GC): A forensic laboratory instrument used to determine the chemical makeup of substances involved in crimes.
- Operational Process: The substance in question is burned at high temperatures, and the specific temperature at which the material vaporizes into gas is charted to identify its exact chemical makeup.
Toxicology: The scientific study of poisons and drugs, focusing on their biological effects on human and animal populations.
Lie Detector (Polygraph): A machine that measures and charts real-time changes in respiration and other physiological bodily functions while questions are posed to a subject.
- Premise: Intentional attempts to provide false answers cause measurable shifts in physiological functions.
- Legal Status: Polygraph results are usually inadmissible in court because many scientists and legal experts consider the outputs to be unscientific and inconsistent.
Composite Drawing: A visual sketch of a suspect created from eyewitness descriptions provided by one or more individuals.