Forensic Science Exam #2

Physiological Biometrics

Based on physical characteristics of the body

Behavioral Biometrics

Based on how a person behaves

Enrollment

The first process that captures a person’s biometric data and stores it in a database for later use

Pre-Processing

Standardizing (preparing and improving) the raw biometric data collected by the sensor before important features are extracted

Feature Extractor (Extraction)

The process of identifying distinctive biometric characteristics that can be used to identify and individual

Template Generator

Saves all the raw data produced by feature extraction and put it into a simple easy-to-read format for the system

Matcher

Compares the test biometric template with one or more stored biometric templates to determine how similar they are

Decision

Takes the matching score produced by the matches and determines the final result

Iris Identification

The iris’ elastic connective tissue (trabecular meshwork) is analyzed, processed into an optical ‘“fingerprint,” and translated into a digital form

Retina Recognition

Captures and analyzes the patterns of blood vessels on the thin nerve on the back of the eyeball that processes light entering through the pupil

The Next Generation Identification System (NGI)

Provides a broader selection of resources and information for law enforcement agencies across the country

Firing Pin Impression

The shape of the firing pin will be impressed into the relatively soft metal of the primer on the cartridge case (shape, size, location of firing pin)

Breech Face Impression

The cartridge case, in its rearward thrust, is impressed with the surface markings of breech face. These striations transfer onto the cartridge and can act like a fingerprint for the firearm.

Rifling

Cutting of curved grooves along barrel, bullets fired are gripped by grooves gives it spin, it improves accuracy and stability of firing

Striations

Markings on the bullet from the inner surface of the barrel

Grooves

The spiral cuts in a rifled bore

Lands

The ridges of metal between the grooves in a rifled bore

Caliber

The diameter of the gun barrel, measured between opposite lands

Bullet Packaging

Wrap it in a tissue paper before placing it in a pillbox or an envelope

Gauge

The diameter of the shotgun barrel

Shot

Shotgun ammunition (shell) contains numerous ball-shaped projectiles

Float Glass

When molten glass is cooled on a bath of molten tin, it is typically used for windows

Tempered Glass

Heated to a high temperature and then rapidly cooled, makes the glass stronger

Laminated Glass

Sandwiching a layer of PVB between two or more layers of glass, used in care windshields

Radial Cracks

Form a right angle on the reverse side of the force

Crack Sequences

A fracture always terminates at an existing line of fracture

Physical Properties

Can be observed without changing a substance into another substance

Chemical Properties

Can only be observed when a substance is changed into another substance

Bromoform

Sinks it is more dense than the liquid

Refractive Index

Ratio of the velocity of light in a vacuum to that in the medium

Refraction

The bending of light waves because of a change in velocity

Becke Line

A bright halo near the border of a particle that is immersed in a liquid of a different refractive index

Match Point

The Becke line disappears and minimum contrast between liquid and particle is observed

Glass Immersion Method

Best used to determine a glass fragment’s refractive index

Trace Elements in Glass

Sand, Soda, Lime

Compound

A pure substance composed of one or more elements

Medulla

Core of hair, useful for species identification, may be absent

Cortex

Embedded with the pigment granules, provide important points of comparison (color, shape, distribution, density)

Cuticle

Outer layer, works as a protective scale (shingles on a roof)

Medullary Index

Measures the diameter of the medulla relative to the diameter of the hair shaft

Comparison Microscope

Indispensable tool for comparing the morphological characteristics go hair

Anagen Phase

Initial phase of growth, follicle actively produces hair, contains follicular tag

Catagen Phase

Transition phase

Telegen

Final growth phase in which the hair naturally falls out of the skin

Follicular Tag

A rich source of nuclear DNA associated with hair

Synthetic Fibers

Produced solely from synthetic chemicals and include nylons, polyesters, and acrylics

Regenerated Fibers

Manufactured from natural raw materials

Comparing Fibers

Cross-sectional shape of the fiber, lengthwise striations on the surface, color, diameter, and presence of declustering particles

IR Microscope

Obtains an infrared spectrum and gives a pattern of peaks, non destructive

HPLC-MS

Identfies compounds by separating dyes and identifying them, destructive

Birefringence

Double refraction when viewed under a polarizing microscope

Flash Point

The lowest temperature at which a liquid will form a vapor

Auto-Ignition Temperature

The lowest temperature at which the fuel will spontaneously ignite

Conduction

The movement of heat through s solid object, creates a new fire location

Flashover

Then autoignition of combustible materials in the room or structure.

Probable Origin

Most likely be the lowest point showing the most intense characteristics of burning

Streamers

Spread the fire from area to another

Indicators of Arson

An irregularly shaped pattern on the floor accelerant onto the surface, discovery of an ignition device accelerant residues

Low Explosives

An explosive with a velocity of detonation less than 1000 meters per second, like black powder or smokeless powder

Deflagration

A very rapid oxidation reaction accompanied by the generation of a low-intensity pressure wave that can disrupt the surroundings

Primary Explosives

A high explosive that is easily detonated by heat, shock, or friction; they are extremely sensitive

Detonation

An extremely rapid oxidation reaction accompanied by a violent disruptive effect and an intense high-speed shock wave