Forensics Final Review - updated 2024

Most Widely Used Illicit Drug in the US

Marijuana

Drugs Derivatives of Opium

Morphine, Heroin, Codeine

Controlled Substances Act

Establishes 5 schedules for controlled substances based on abuse potential, dependence, and medical value. Allows AG to add, delete, or reschedule drugs. Imposes manufacturing quotas and outlines penalties.

Color Tests for Marijuana and Cocaine

Marijuana: Duquenois-Levine Test (turns purple); Cocaine: Scott Test (liquids turn blue, then pink, then back to blue)

Highest Magnification with Compound Microscope

400x

Relationship between Magnification and Field of View

Inversely proportional - higher magnification, smaller field of view

Parts of the Hair Shaft

Cuticle, Medulla, Cortex

Most Resistant Part of Hair Shaft to Chemical Decomposition

Cuticle

Important Features for Determining Species of Hair

Cuticle Scale Pattern & Medulla Pattern

Central Canal in Hair Shaft

Medulla

Different Patterns in a Medulla

Absent, Continuous, Interrupted, Fragmented

Nuclear DNA Typing on Hairs

Anagen phase or very beginning of Catagen phase

Most Prevalent Natural Plant Fiber

Cotton

Crimes Involving Paint as Key Evidence

Hit and Run; Burglary

Role of a Toxicologist

Detect and identify unknown toxins in the body system

Where does alcohol come from?

Fermentation of wheat products

Meaning of BAC

Blood Alcohol Content

Factors Influencing Alcohol Absorption Rate

Sex, weight, type of alcohol, time frame, food eaten prior

Organs Absorbing Alcohol into Bloodstream

Stomach and Small Intestine

Relationship Between Blood Alcohol and Alveolar Breath

True; this is why a breathalyzer test works!

Name two Field Sobriety Tests

Eye Nystagmus; Walk and Turn

Maximum BAC for Truck/Bus Drivers

0.04%

Time for Alcohol Concentration to Peak under normal drinking conditions

2-3 hours after last drink

Natural processes for alcohol removal from the body

Oxidation and Excretion (sweating, breathing, urinating)

Main Blood Components for Blood Identification

RBC (Red Blood Cells) and Blood Serum

Antigens for Compatibility Testing

A, B, and D

Location of Antigens in the body

On the surface of RBCs

Location of Antibodies in the body

In the blood serum

Main Purpose of RBC in the body

Transport oxygen and remove carbon dioxide

Antigens & Antibodies for Blood Types (A, B, AB, O)

Type A: A antigens, B antibodies; Type B: B antigens, A antibodies; AB: A, B antigens, No antibodies; O: No antigens, A, B antibodies

How is Blood Stain Shape useful in Crime Scene Investigation?

Provides information on direction, dropping distance, and angle of impact of splattered blood

What is the Basic Unit of Heredity?

Gene

How many Chromosomes do non-reproductive cells have?

23 pairs, 46 chromosomes

Who determines the Sex of the Offspring?

Biological Father (sperm: X or Y; egg: X; XX = female, XY = male)

Possible Genotypes and Phenotypes of offspring from A and B blood types?

A, AB, B, O *Remember to consider AA, AO, BB, BO possibilities*

Can a Type B mother and Type B father have a Type O child?

Yes

What does DNA stand for?

Deoxyribonucleic acid

Where is DNA located in the body?

In nucleus of all cells except red blood cells; also in mitochondria

DNA is classified as which macromolecule?

Polymer

What are the building blocks of DNA?

Nucleotides

Composition of Nucleotides

Deoxyribose sugar, phosphoric acid, nitrogen bases (adenine, thymine, cytosine, guanine)

Shape of DNA

Double helix

Complementary Nitrogen Base Pairs

A/T and G/C

Function of DNA

Controls production of proteins, hormones, etc

Definition of Codon

Sequence of 3 bases that code for a specific amino acid

Process of DNA Replication

Begins with unwinding of double helix, separation of strands exposing nitrogen bases; free nitrogen bases attach to complement; results in 2 identical strands. Requires helicase, polymerase, and ligase enzymes.

Function of Restriction Enzymes

Cuts DNA after a specific sequence of bases (codon)

Function of PCR

Produces many exact copies of DNA segments

Function of Gel Electrophoresis

Separates DNA pieces based on charge and size

Function of STR

Helpful DNA markers consisting of 3-7 bases; ideal for PCR amplification due to small size

Why is Mitochondrial DNA Important in Forensic Science?

More resilient to degradation; more abundant in cells; relates victim back to maternal side of the family

What is CODIS?

Combined DNA Index System

Definition of Forensic Science

Application of science to civil and criminal laws

Metric Prefix Line and Relationships

G (giga, 10^9) M (mega, 10^6) k (kilo, 10^3) h (hecto, 10^2) da (deka, 10^1) base unit (g, m, L) d (deci, 10^-1) c (centi, 10^-2) m (milli, 10^-3) µ (micro, 10^-6) n (nano, 10^-9) p (pico, 10^-12)

Expert Witness Role and Importance

Higher level degree in a specific area; testify in court; e.g., psychologist studying serial killers

Chain of Custody

List of people who handled specific evidence

Methods for Recording a Crime Scene

Photographs, notes, sketches

Methods for Searching a Crime Scene

Spiral, Line, Grid, Quadrant Search

Importance of Reference/Control Sample

Used for comparisons; e.g., blood/DNA of suspects compared to crime scene sample

Crime Scene Reconstruction

Uses evidence to determine how crime occurred; includes medical examiner reports and eyewitness testimony

Algor Mortis, Livor Mortis, Rigor Mortis

Algor Mortis: reduction in body temperature post-death; Livor Mortis: blood settling in body post-death; Rigor Mortis: muscle stiffening post-death. *Help determine time of death.*

4th Amendment and Evidence Removal

4th Amendment outlines procedures for evidence removal from crime scenes.

Exceptions to Search Warrant Requirement

No warrant needed for medical emergencies, imminent evidence destruction, or during a legal arrest.

Class vs. Individual Characteristics

Class: narrows search to group (e.g., blood type); Individual: narrows search to one person (e.g., DNA).

Fingerprint Formation

Fingerprints form in-utero during fetal development.

Latent Fingerprints

Not visible fingerprints requiring techniques like dusting or chemical treatment to reveal.

Ridge Patterns and minutiae

Basic ridge patterns: loop, whorl, arch. *Minutiae like ridge endings, bifurcations are used for comparison.*

Fingerprint Analysis Techniques

Techniques include super glue fuming, iodine fuming, ninhydrin, physical developers, dusting with powders, etc.

what type of solid is glass

Glass is an amorphous solid with no specific atomic arrangement.

Types of Conchoidal Fractures

Radial and Concentric fractures

Which type of Conchoidal Fracture occurs first?

Radial fractures occur 1st on the side opposite the force. 3 R Rule - Radial fractures occur at Right Angles on the Reverse side of the force

On which side of the glass does the first fracture occur?

Radial fractures occur on the side of the glass that is opposite of the force.

Where do Concentric Fractures occur?

Concentric fractures occur on the glass on the same side as the force.

Difference between Entrance and Exit Holes/Wounds from a Bullet

Exit wound from a bullet will be much larger.

According to entomologists, who is the 1st witness to arrive at a crime scene?

Blowfly

What do the following areas of forensic science study:

odontology? serology? anthropology? toxicology?

odontology - teeth

serology - blood and bodily fluids

anthropology - bones

toxicology - toxins/poisons/drugs found in bodily fluids, tissues, blood, etc.

Who is responsible for determining which pieces of evidence will be admissible in court?

trial judge

What are the 5 different manners of death?

Homicide, Suicide, Natural, Accidental and Undetermined

Under what circumstances does a police officer not need a search warrant?

No warrant is needed if there is someone in need of medical attention, if evidence is in imminent danger of being destroyed, if given permission to search by the people who own the private property, or if the officer is in the process of a legal arrest

Which fingerprint ridge pattern is the most common?

Loop

Which pieces of minutiae are the most common?

ridge endings and bifurcations

Which 2 factors can affect the refractive index of a piece of glass?

Wavelength or color of light passing through the glass

Temperature

What technique is used to analyze soil?

density gradient tube

What are the different types of microscopes?

compound, comparison, stereoscopic, microspectrophotometer, polarizing and scanning electron

What type of evidence does a compound microscope best analyze?

hairs and fibers

What type of evidence can a comparison microscope analyze?

2 fingerprints, 2 bullets, 2 hairs, etc to see if they are a match

What type of evidence can a stereoscopic microscope analyze?

larger items like a tool or piece of clothing

What type of evidence can a polarizing microscope analyze?

birefringent minerals in soil; synthetic fabrics

What type of evidence can a SEM analyze?

gunshot residue; tiny specimens that require high magnification

What type of evidence can a microspectrophotometer analyze?

chemical composition of paint chips