Forensic Science I Midterm Review

Comprehensive vocabulary flashcards covering fundamental forensic science concepts, firearm and toolmark identification, trace evidence, bloodstain pattern analysis, forensic pathology, legal doctrines, and landmark forensic cases based on the midterm review.

Forensic Science

The application of science and technology to questions arising in criminal or civil matters.

Due Process

Constitutionally fair government procedures required before depriving an individual of life, liberty, or property, anchored in the Fifth and Fourteenth Amendments.

Burden of Proof (Criminal Trial)

The legal obligation placed on the prosecution to establish every required element of an offense beyond a reasonable doubt.

Presumption of Innocence

The legal doctrine that the accused begins trial presumed innocent and is not required to prove their innocence.

Chain of Custody

A comprehensive documented record of evidence collection, possession, transfers, storage, testing, and handling intended to establish that the exhibit is the same item collected and has not materially changed or been substituted.

Admissibility versus Weight

Admissibility governs whether evidence may be introduced in court (decided by the judge), whereas weight refers to the persuasiveness of the evidence (assessed by the factfinder).

Known Sample (Reference Sample)

Material obtained from an established, verifiable source used to compare against questioned evidence.

Questioned Sample

Evidence or material whose original source, origin, or identity is under active investigation.

Direct Evidence versus Circumstantial Evidence

In standard legal usage, direct evidence establishes a fact without an intervening inference, while circumstantial evidence requires an inference to connect the evidence to a fact in issue.

Collateral Evidence

Background information regarding a subject's lifestyle, habits, or interests that does not directly link them to the specific crime scene or criminal act.

IBIS

Integrated Ballistic Identification System; an automated system that compares digital ballistic images to produce candidate associations for firearm examiners.

NIBIN

National Integrated Ballistic Information Network; a nationwide U.S. ballistic imaging network that connects firearm-related evidence across different jurisdictions.

Comparison Microscope

An optical device consisting of two microscopes linked by an optical bridge, permitting the side-by-side comparative examination of two items, such as fired bullets or cartridge cases.

Caliber

The nominal bore diameter of a firearm or diameter of a projectile, commonly designated in fractions of an inch or in millimeters; functions as a class characteristic.

Rifling

Helical spiral lands and grooves cut or formed inside a firearm barrel to impart gyroscopic stability and spin to a fired bullet.

Lands and Grooves

Lands are the raised surfaces inside a rifled barrel; grooves are the cut or recessed channels between the lands.

Ballistics (Internal, External, Terminal)

Internal ballistics covers processes inside the firearm; external ballistics encompasses the projectile's flight through the air; terminal ballistics addresses projectile impact and damage on the target.

Powder Stippling versus Soot

Soot is a superficial carbon deposit on a surface that can wipe away, while stippling (tattooing) results from unburned and burning powder particles physically striking and embedding in the skin.

Locard's Exchange Principle

The foundational forensic concept that whenever two items or individuals come into contact, a mutual cross-transfer of physical material can occur.

Randomly Acquired Characteristics (RACs)

Individualizing features that develop randomly over time due to wear, use, damage, or manufacturing imperfections, such as cuts, nicks, or scratches on an outsole or tool.

Physical Fit (Jigsaw Match)

The mechanical alignment of two or more fractured, torn, or separated fragments, demonstrating that they previously formed a single contiguous object.

Cast-off Pattern

A bloodstain pattern created when blood droplets are projected from an object in motion, such as a swung weapon or limb.

Impact Spatter

A bloodstain pattern produced when an energy-bearing object forcefully strikes an existing source of exposed liquid blood, breaking it into small droplets.

Arterial Gush / Spurt Pattern

Bloodstain distribution resulting from the escape of blood under dynamic systemic pressure from a damaged artery, characteristically displaying pulsatile or wave-like configurations.

Void Pattern

An absence of bloodstains within an otherwise continuous blood spatter distribution, indicating an intervening object blocked the deposition of droplets.

Swipe Pattern

The transfer of blood onto an unstained surface caused by the lateral movement of a blood-bearing object across that surface.

Wipe Pattern

A bloodstain pattern created when a clean or secondary object moves through and alters an existing wet bloodstain.

Satellite Stains

Smaller blood droplets that separate from a larger parent drop during impact and land around the central parent stain.

Skeletonized Stain (Perimeter Stain)

A bloodstain retaining its outer dried boundary after the moist, central portion of the stain has been removed by wiping, flaking, or smearing.

Bloodstain Angle of Impact

The acute angle formed between the trajectory of a blood drop and the plane of the target surface, calculated using $\text{Angle} = \text{arcsin}\left(\frac{\text{width}}{\text{length}}\right)$ using the parent ellipse.

Area of Convergence versus Area of Origin

The area of convergence is a two-dimensional intersection of blood flight lines on a flat plane; the area of origin is the three-dimensional location in space from which the blood originated.

Luminol

A presumptive chemical reagent that produces chemiluminescence when reacting with the iron present in hemoglobin derivatives.

Hair Morphology (Cuticle, Cortex, Medulla)

The cuticle is the external protective scale layer; the cortex is the central protein core containing pigment granules; the medulla is the inner cellular canal.

Radial versus Concentric Cracks

Radial cracks extend outward like spokes from the primary point of impact; concentric cracks form rough circular rings centered around that impact point.

Glass 4R Rule

A forensic rule determining force direction on non-tempered glass: Ridges on Radial fractures form Right angles to the Rear (opposite the impact surface).

Automotive Paint Layer Sequence

The standard factory finishing order consisting of: electrocoat primer, primer surfacer, base/color coat, and clearcoat.

Primer GSR Composition

Traditional gunshot residue composed of lead (from lead styphnate initiator), barium (from barium nitrate oxidizer), and antimony (from antimony sulfide fuel).

Laceration

A ragged blunt-force tear in cutaneous and subcutaneous tissue caused by crushing, stretching, or shearing, frequently exhibiting tissue bridging and irregular margins.

Incised Wound

A sharp-force cut produced by a sharp-edged instrument that is longer on the skin surface than it is deep.

Stab Wound

A penetrating sharp-force injury caused by a pointed instrument that extends deeper into body tissues than the length of its external skin incision.

Tissue Bridging

Intact strands of nerves, blood vessels, and fibrous connective tissue that span across the floor of a blunt-force laceration, distinguishing it from an incised wound.

Contusion

A blunt-force injury (bruise) characterized by the rupture of sub-epidermal capillaries and blood vessels beneath intact skin.

Abrasion

A superficial scrape or friction injury resulting in the denudation of the outer epidermal layers of the skin.

Penetrating versus Perforating Gunshot Wound

A penetrating gunshot wound enters an anatomical structure or body without exiting; a perforating gunshot wound enters and completely traverses the structure, creating both entrance and exit defects.

Permanent Cavity versus Temporary Cavity

The permanent cavity is the physical tunnel of pulverized tissue directly along the bullet's path; the temporary cavity is the radial stretching and displacement of surrounding tissue caused by hydrodynamic shockwaves.

Imminent Danger (Deadly Force)

An impending or immediate threat of death or serious bodily harm, judged from the perspective of an objectively reasonable officer based on circumstances known at the time.

Reasonable Expectation of Privacy (Katz Test)

A Fourth Amendment doctrine requiring that an individual exhibit an actual subjective expectation of privacy and that this expectation be one that society is prepared to recognize as reasonable.

Curtilage versus Open Fields

Curtilage is the immediate area surrounding a dwelling that harbors the intimate activities of home life (afforded high Fourth Amendment protection); open fields are unoccupied or undeveloped lands lacking constitutional protection.

Plain-View Doctrine

An exception allowing law enforcement to seize evidence without a warrant if the officer is lawfully positioned, has lawful physical access, and the incriminating nature of the item is immediately apparent.

Exclusionary Rule

A judicially created rule requiring that evidence collected in direct violation of a defendant's constitutional rights under the Fourth Amendment be suppressed from criminal trial proceedings.

Fruit of the Poisonous Tree

An evidentiary rule that extends the exclusionary rule to suppress any secondary or derivative evidence discovered as an indirect result of an initial illegal search or seizure.

Patent, Plastic, and Latent Fingerprints

Patent prints are visible friction ridge impressions made in transferred fluids (such as blood or paint); plastic prints are 3D indentations molded into malleable surfaces; latent prints are invisible deposits of natural secretions requiring visualization.

Minutiae (Galton Details)

Individual friction ridge path characteristics, such as ridge endings, bifurcations, dots, and islands, utilized to compare and individualize fingerprint impressions.

Investigative Genetic Genealogy (IGG)

An investigative workflow that combines advanced DNA analysis with genealogical database matches and public-record research to construct family trees and generate investigative suspect leads.

McHoul Test

The Massachusetts standard for criminal responsibility establishing that an individual is not responsible if, due to a mental disease or defect, they lacked substantial capacity either to appreciate the wrongfulness of their conduct OR to conform their conduct to the requirements of the law.