Forensic Science and Physical Evidence

Comprehensive vocabulary flashcards covering the key principles of forensic science, crime scene processing, dactyloscopy, bloodstain pattern analysis, ballistics physics, ink chromatography, and forensic anthropology.

Forensic Science

The application of scientific techniques to answer questions of interest to a crime and provide evidence for court cases, derived from the Latin forensis, meaning "of or before the forum."

Edmond Locard

A French criminologist known as "The French Sherlock Holmes" who opened the first police laboratory in Lyon in 1910 and formulated the core forensic tenet that "every contact leaves a trace."

Locard's Exchange Principle

The principle stating that every time a person comes into contact with a place or another person, something of that first person is left behind and something of that place is taken away.

Testimonial Evidence

Evidence consisting of oral or written statements provided to police or delivered in court testimony by individuals who witnessed an event.

Physical Evidence

Any material, tangible items found at a crime scene, on a victim, or in the possession of a suspect.

Trace Evidence

Physical evidence present in small but measurable quantities, including strands of hair, clothing fibres, skin cells, gunshot residue, glass, or soil.

Post-Mortem Interval (PMI)

The length of time that has elapsed since an individual's death, estimated by a forensic pathologist using body cooling, rigor mortis, skin discoloration, decomposition stage, and insect activity.

Dactyloscopy

The scientific study and analysis of fingerprints for personal identification.

Latent Prints

Invisible fingerprint impressions formed when perspiration, skin cells, proteins, and oils are deposited on an object, requiring physical powder dusting or chemical visualization to be seen.

Patent Prints

Easily visible fingerprints left on a surface after a finger comes into contact with a liquid medium such as wet blood, paint, or ink.

Plastic Prints

Three-dimensional fingerprint impressions pressed into soft, pliable substances such as clay, putty, or wax.

Bifurcation

A fingerprint minutiae characteristic where a single friction ridge divides into two separate ridges.

Ninhydrin

A chemical reagent sprayed onto porous substrates such as paper or fabric that reacts with amino acids in fingerprint residue to produce a purple-coloured compound.

Superglue Fuming

A method of developing latent fingerprints in an enclosed chamber using cyanoacrylate ester vapors that condense onto friction ridges to form durable white prints.

Ten-Print Card

A standardized form used to collect reference ink impressions of all ten fingers, rolled from cuticle to cuticle, for suspect identification and cataloging.

Bloodstain Pattern Analysis

The examination of the shapes, distribution, and locations of bloodstains to reconstruct the physical events and forces responsible for their creation.

Passive Bloodstains

Blood drops, drips, and pools formed exclusively under the influence of gravitational force acting alone on liquid blood.

Swipe

A transfer bloodstain pattern formed when blood is wiped from a moving, blood-bearing source onto an unstained surface, often displaying a feathered edge indicating direction.

High Velocity Impact Spatter (HVIS)

A fine bloodstain misting pattern caused by high-energy impacts, such as gunshots or high-speed machinery.

Arterial Spurting Pattern

A bloodstain pattern featuring gushes or spurts created when blood exits the body under pressure from a severed or breached artery.

Bloodstain Direction of Travel

The orientation and path of a blood drop as it strikes a surface at an acute angle, indicated by an elongated stain whose narrow tail or projection points in the direction of motion.

Ballistics

The forensic science dealing with the launching, flight behavior, trajectory, and impacts of projectiles such as bullets.

Rifling

Spiral grooves and lands cut inside a gun barrel that impart rotational spin to a bullet to stabilize its flight path.

Striation Marks

Microscopic scratch lines carved onto a bullet's outer casing as it passes through the barrel, creating an individualized pattern that can match a projectile to a specific firearm.

Inertia

The natural property of an object to resist changes in its velocity or state of rest, as stated in Newton's First Law of Motion.

Newton's Second Law of Motion

The principle stating that the net force applied to an object is equal to its mass multiplied by its acceleration, represented by $F = m \times a$.

Newton's Third Law of Motion

The physical law stating that when two objects interact, they apply equal and opposite forces onto each other; for every action, there is an equal and opposite reaction.

Speed

A scalar measurement indicating the rate at which an object covers distance over time, calculated as $\text{speed} = \frac{\text{distance}}{\text{time}}$.

Velocity

A vector quantity indicating both the rate of positional displacement over time and the physical direction of travel, calculated as $v = \frac{x}{t}$.

Acceleration

The rate of change in an object's velocity per unit of time, calculated using the formula $a = \frac{v - u}{t}$, where $v$ is final velocity and $u$ is initial velocity.

Questioned Documents

Written or printed communications whose origin, authorship, or authenticity is unknown or under legal dispute, such as extortion letters or altered documents.

Chromatography

A chemical technique used to separate and isolate the individual pigment components of a mixture, such as document inks, across stationary and mobile media.

Mobile Phase

The moving liquid solvent, such as water or ethanol, that travels up the chromatography substrate and carries ink components.

Stationary Phase

The solid material, such as paper or a thin layer plate, onto which chemical pigments adsorb during chromatography separation.

Retention Factor ($R_f$)

The ratio of the distance traveled by an individual chemical component to the distance traveled by the solvent front, calculated as $R_f = \frac{\text{distance traveled by component}}{\text{distance traveled by solvent front}}$.

Anthropometry

An identification system established by Alphonse Bertillon in the late 1800s that uses precise, recorded anatomical bone dimensions to identify individuals.

Forensic Anthropology

The branch of science that analyzes skeletal remains to determine an individual's identity, biological sex, age, estimated height, and cause of death.

Pubic Arch

An anatomical feature of the pelvis used in skeletal sex determination; it forms an acute angle of $60^\circ - 70^\circ$ in males and a broader angle of $80^\circ - 90^\circ$ in females.

Mastoid Process

A bony projection of the temporal bone located behind the ear that is noticeably larger and more prominent in male skulls than in female skulls.