Forensic Science 1-Exam 2-University of Southern Mississippi

What are the two main types of fingerprints?

Known fingerprints and unknown fingerprints.

What does ACE-V stand for in fingerprint analysis?

Analysis, Comparison, Evaluation, and Verification.

What is AFIS?

Automated Fingerprint Identification System — a database used to compare and identify fingerprints.

How are fingerprints used in forensic science and criminal justice?

For identification of criminal offenders and decedents, and as common, versatile physical evidence.

What makes fingerprint evidence versatile?

It can be processed using multiple techniques.

What is friction ridge skin?

The hairless skin found on the palms of the hands and soles of the feet that contains the highest concentration of sweat glands.

What are known fingerprints?

Fingerprints of an identified individual that are deliberately recorded; also known as exemplars.

What is the first principle of fingerprints?

Permanence — friction ridge patterns form during fetal life and remain unchanged until decomposition.

What is the only exception to fingerprint permanence?

Permanent scarring.

What is the second principle of fingerprints?

Uniqueness — no two fingerprints are identical, even among identical twins.

What are the three levels of fingerprint detail?

Level 1: Ridge Flow (Pattern Types)

Level 2: Ridge Path (Minutiae)

Level 3: Ridge Shape (Edges and Pores)

What are the three main fingerprint pattern types?

Arch (5%), Loop (60-65%), and Whorl (30-35%).

What are the two types of loops?

Ulnar (opens toward pinkie) and Radial (opens toward thumb).

What are minutiae?

Small ridge characteristics such as bifurcations, ridge endings, and dots that make each fingerprint unique

What determines fingerprint uniqueness?

The amount, location, and spatial relationship of minutiae.

What are unknown fingerprints?

Partial reproductions of friction ridge skin left on an object by chance.

What are the three types of unknown prints?

Latent, patent, and plastic prints.

What are latent prints?

Invisible prints made by oils or perspiration from the skin.

What are patent prints?

Visible prints made with substances like blood, grease, or mud.

What are plastic prints?

Three-dimensional prints left in a soft surface like wax, clay, or soap.

What factors affect print processing?

Type of print, substrate (porous or non-porous), resources, and order of operations.

What are the three major categories of processing techniques?

Optical (photography)

Physical (powders)

Chemical (superglue, dye stains)

What can fingerprints tell investigators?

That a person touched an item.

What can fingerprints NOT tell investigators?

When, how, age, gender, or race of the person who touched the item.

What does the absence of fingerprints mean?

It doesn't necessarily mean someone didn't touch an item.

What is the first stage of the ACE-V methodology?

Analysis — examiner evaluates print clarity, pressure, and detail based on experience.

What is noted during the Analysis stage?

Substrate, development medium, deposition pressure, motion distortion, clarity, and anatomical area.

What is the Comparison stage?

Direct comparison between known and unknown prints, including use of databases.

What happens during Evaluation?

Examiner determines if the prints are from the same source (identification), different sources (exclusion), or inconclusive.

What is Verification in ACE-V?

Independent re-examination by another qualified examiner to confirm or refute the findings.

What are the three possible conclusions in fingerprint evaluation?

Identification, Exclusion, or Inconclusive.

What is the purpose of AFIS?

To compare fingerprint data using computerized matching at local, state, and federal levels.

What are the two main AFIS databases?

Known Database (finger and palm prints) and Latent Database (examiner-plotted prints).

What are the three AFIS search types?

Blind Search: latent against all known prints

Direct Search: latent against one person's prints

Reverse Search: known prints against all unidentified latents

What is a limitation of AFIS?

It doesn't automatically identify suspects — trained examiners interpret the results.

What does "Garbage in = Garbage out" mean in AFIS?

Poor quality known prints lead to poor search results and unreliable matches.

What is the main purpose of firearms identification?

To determine whether a bullet or cartridge was fired by a particular weapon.

What does AFTE stand for?

Association of Firearm and Tool Mark Examiners.

What does AFTE provide for examiners?

Professional certification and standards for firearm and tool mark analysis.

What are the three main types of handguns?

Single-shot pistols, revolvers, and semi-automatic pistols.

How many rounds do handguns fire at a time?

One round per trigger pull.

What are single-shot pistols?

Handguns that fire only one round before reloading.

What is a revolver?

A handgun with multiple firing chambers in a revolving cylinder.

What are the three types of revolvers?

Swing-out, break-top, and solid-frame.

What is a swing-out revolver?

A revolver with a cylinder that swings out to the side for loading.

What defines a semi-automatic pistol?

It uses a removable magazine and fires one shot per trigger pull.

Do semi-automatic pistols use clips or magazines?

Magazines (not clips).

What are long guns?

Firearms designed to be fired from the shoulder, such as rifles and shotguns.

What are the two main types of long guns?

Rifles and shotguns.

What does rifle ammunition consist of?

Single bullets impressed with lands and grooves during firing.

What does shotgun ammunition consist of?

Shot shells containing multiple small pellets called shot.

What is the purpose of a shotgun choke?

It narrows the barrel to concentrate the shot when fired.

What is the difference between a rifle and a shotgun barrel?

Rifles have rifled barrels (lands and grooves); shotguns have smooth barrels.

What is shotgun gauge?

The barrel diameter measurement; higher gauge = smaller barrel diameter.

Why can shotgun pellets rarely be matched to a specific gun?

They lack unique rifling marks.

What happens when a gun is fired?

Trigger pulled → firing pin hits primer → primer ignites gunpowder → gases expand → bullet propelled → cartridge pushed back.

What propels the bullet through the barrel?

Expanding gases from burning gunpowder.

What creates unique barrel markings on bullets?

The microscopic imperfections from manufacturing (lands and grooves).

How is a gun barrel made?

By drilling a solid steel bar, leaving random microscopic drill marks.

What is rifling?

Spiral grooves inside the barrel that spin-stabilize the bullet.

What are three ways rifling is formed?

Broach cutting, button pressing, and hammer forging.

What are lands and grooves?

Lands are raised areas; grooves are recessed areas that twist down the barrel.

What is caliber?

The diameter of the barrel measured between opposite lands.

What are striations?

Fine lines from imperfections in the rifling that mark each bullet uniquely.

What are class characteristics of a firearm?

Features common to a model or manufacturer (e.g., number and direction of grooves).

What are individual characteristics of a firearm?

Unique microscopic marks (striations) caused by manufacturing and wear.

What is used to compare bullets microscopically?

A comparison microscope.

What are the initial points of comparison between bullets?

Number of lands/grooves and direction of twist.

What happens if class characteristics differ?

The bullets could not have come from the same gun.

What if class characteristics are the same?

Individual characteristics are compared to determine a match.

What is the goal of firearm comparison?

Individualization — linking a bullet to a specific firearm.

What firearm components can leave marks on cartridge cases?

The firing pin, breechface, extractor, and ejector.

How does the firing pin leave a mark?

It strikes the primer, leaving its shape impressed in the metal.

What does the extractor do?

Pulls the spent cartridge from the chamber.

What does the ejector do?

Expels the cartridge case from the firearm.

What marks does the breechface leave?

Surface impressions on the rear of the cartridge case from recoil.

What is NIBIN?

National Integrated Ballistics Information Network — database of bullet and casing images.

What is the purpose of NIBIN?

To link ballistic evidence from different crimes or firearms.

Who confirms a NIBIN match?

A trained firearms examiner using a comparison microscope.

What is IBIS?

Integrated Ballistics Identification System — digital imaging used in NIBIN for comparison.

What is distance determination?

Estimating how far the gun was from the target when fired.

How is distance determination tested with a suspect weapon?

By comparing residue on evidence with test shots at known distances.

What are the signs of a contact shot (less than 1 inch)?

Star-shaped tear, smoke ring, scorching, or melted fabric.

What residue appears at 12-18 inches?

Vaporous lead and partially burned powder grains.

What is seen at 25-36 inches?

Partially burned powder but no soot.

What is seen at 3 feet or more?

No powder residue, possibly a dark bullet wipe ring.

How is shotgun distance determined?

By measuring pellet spread — wider spread means greater distance.

What is gunshot residue (GSR)?

Tiny particles from gunpowder and primer that land on hands, clothes, and the target.

What elements are analyzed in GSR tests?

Barium and antimony.

What equipment detects and identifies GSR particles?

Scanning Electron Microscope (SEM).

What part of the hand is tested for GSR?

The thumb web, back of hand, and palm.

Why restore serial numbers on firearms?

To identify weapons whose serial numbers were removed or altered.

How are serial numbers restored?

By chemical etching — strained metal beneath the surface reacts differently.

Why does chemical etching work?

The metal crystals beneath stamped numbers remain permanently deformed.

How should a firearm be handled at a crime scene?

By gripping the trigger guard edge or checkered portion of the grip.

What must be done before sending a firearm to the lab?

Unload and secure it to prevent accidental discharge.

What must be recorded when collecting a revolver?

The position of each chamber and which cartridges were fired.

How should bullets and casings be packaged?

Individually, wrapped in tissue to protect markings, and placed in labeled containers.

What is a tool mark?

Any impression, cut, gouge, or abrasion made by a tool contacting another object.

What do tool marks reveal?

Class characteristics (size/shape) and individual characteristics (unique wear patterns