Forensics Exam 2

Elements

Basic chem subs that make up all matter and cannot be broken down into simpler substances.

Compound

A chem sub made of two or more elements

Solids vs Liquids vs Gases

S: definite shape and volume and particles that vibrate in place

L: definite volume, takes shape of container

G: no definite shape or volume, expands to fill container

Phase

Separation of a mixture into its compounds based on the distribution of the two subs

Organic vs Inorganic Compounds

Organic comps include all carbon, oxygen, and hydrogen Inorganic comps don’t

Qualitative vs Quantitative Analysis

Type of subs present vs How much of sub

How does liquid reach equilibrium with its gaseous phase (Henry’s Law)

At a constant temperature, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid (more gas pressure, more gas dissolves in liquid)

 Process of Chromatography  

Separating a mixture into its components and passing through a stationary phase as a mobile phase

Parts of Gas Chromatograph (GC)

Gas flows through column, stationary phase is film of liquid in column spiral, separated into its components by the stationary phase

Retention Time

Time required for component to emerge from GC column

Thin-layer (TLC) vs Gas Chromatography (GC)

TLC uses a liquid mobile phase and solid stationary phase GC uses a gas mobile phase and a solid stationary phase

Rf Value (retention factor)

How far a sub travels relative to the solvent (component traveled / solvent traveled)

Electrophoresis

Technique that forces materials to move across a gel-covered plate under electrical potential (charge)

Wave vs Particle Theories of Light

Wave: continuous wave

Particle: stream of discrete energy particles

Electromagnetic Spectrum

Entire range of radiation energy

Relationship between color and the absorption of light by molecules

The specific color it absorbs identifies exactly what the compound is made up of

Beer’s Law

The amount of light a sub absorbs is directly proportional to its concentration

Parts of simple Absorption Spectrophotometer

Radiation source, sample holder, frequency selector, detector from electromagnetic radiation to electric signals, recorder to make record of signal

UV and IR absorption spectrum use for identifying organic comps

Each absorption acts as a “fingerprint” of a sub directly identifying it

Concept of Mass Spectrometry

The identification of each chem by a high-energy electron beam that makes positively charged ions (cation)

Significance of Mass Spectrum

Identifying unknown subs and finding its abundance

Usefulness of Trace Evidence for type of physical evidence

Helps establish the source of physical evidence by making it individual evidence

Continuous vs Line Emission Spectrum

Protons vs Electrons vs Neutrons

P: positively charged, large mass

E: negatively charged, small mass
N: no charge, large mass

Atomic Number and Atomic Mass Number

A#: # of protons

AM#: # of protons and neutrons combined

Orbital Energy Levels

Regions in atoms where there is a high probibility of finding an electron

What happens when an atom absorbs a certain amount of energy

They become “excited,” higher, and more unstable

Atom releasing energy in light form

Releasing a photon

Isotope

Atoms with same # of protons but different # of neutrons creating different atomic masses

Radioactivity

Emission of electromagnetic energy particles

How can elements become radioactive

By losing or gaining a neutron making a different isotope

Why are X-ray Diffraction patterns useful for chem identification

Used for solid and crystalline structures, there are different patterns for each element, making them “fingerprints”

Psychological vs Physical Dependance

Psy: an emotional and metal craving for a high

Phys: an adaption to the drug causing withdrawal without it

Controlled Substances Act Schedules

I: high risk for abuse and no accepted medical use; heroin, LSD

II: high risk and medical use with severe restrictions; cocaine, PCP, amphetamines

III: less risk and current medical use; codeine

IV: low risk and current medical use; darvon, tranquilizers

V: low risk and common medical use; opiates, nonnarcotics

Lab Tests for Identifying Drugs

Screen test by color and property (pill, powder, liquid) and then use NIK flow chart with small amount to identify common drugs

Proper Collection of Drugs

Prevent loss, label correctly, cause no cross-contamination, original container can suffice

Individuals who made significant contributions to fingerprinting

Francis Galton: wrote a fingerprinting book

Juan Vucetich: created a workable system and solved first murder case with fingerprints

Sir Edward Henry: created categories of fingerprints based of order and type of patterns

Ridge Characteristics

ridge ending, bifurcation, trifurcation, dot, island,

Fingerprint Classes

Loop: ulnar (pinky), radial (thumb)

Whorl: plain, accidental, double, and central pocket loop

Archs: plain and tented

IAFIS

Integrated Automated Fingerprint Identification System

Visible vs Plastic vs Latent Prints

Visible: fingerprint in liquids

Plastic: fingerprints in soft solids (soap bars, putty)

Latent: oils and water left from fingers of solid surface

Types of Fingerprint Development

Powder (volcanic ash and magnetic): nonporous solid surfaces (glass, tile)

Super Glue Fuming: nonporous surfaces that are movable (leather, plastics)

Iodine Fuming and Ninhydrin: porous surfaces (paper, cloth)

How to Preserve Prints

Take pictures before removing and lifting with tape and transporting it to a labeled paper card