Blood Stain Pattern Analysis and Forensic Serology

Vocabulary flashcards covering key concepts from Blood Stain Pattern Analysis, Forensic Serology, DNA analysis, and related topics.

Blood Stain Patterns

The four main types are Spatter, Transfer, Swipe, and Wipe.

Spatter Patterns

They are generally caused by force applied to a blood source.

Forward Spatter

In relation to the force, this spatter travels in the same direction as the force.

Backward Spatter

In relation to the force, this spatter travels opposite the direction of the force.

Surface Texture - Hard non-porous surface

The resulting bloodstain looks smooth, circular, with minimal spatter.

Surface Texture - Rough surface

The resulting bloodstain has an irregular shape, may have satellite spatter or distortion.

Blood Direction

The pointed end of an elongated bloodstain indicates the direction of travel.

Size of Blood Drop

Larger drops tend to travel further due to greater mass and momentum.

Gunshot Spatter - Forward

Fine mist traveling in the same direction as the bullet.

Gunshot Spatter - Backward

Mist-like spatter traveling back towards the shooter.

Castoff Spatter

Caused by blood flung off a moving blood-bearing object.

Documenting Blood Stain Evidence

Key aspects include photography, sketches, notes on location, size, shape, distribution, and pattern type.

Psychological Dependence

A condition where a person believes they need a drug to feel normal or cope emotionally.

Physiological Dependence

A condition where the body has adapted to a drug's presence, causing withdrawal symptoms upon cessation.

Neurotransmitters

Found in the synapse; they transmit signals from one neuron to another.

Endorphins

Natural pain relievers and mood elevators.

Acetylcholine

Involved in muscle contraction, memory, and learning.

Dopamine

Involved in reward, motivation, and motor control.

GABA

The primary inhibitory neurotransmitter in the brain, calming nervous activity.

Serotonin

Involved in mood, sleep, appetite, and regulation of emotions.

Ligand

A molecule that binds to a receptor.

Agonist

A ligand that binds to a receptor and triggers a biological response.

Antagonist

A ligand that binds to a receptor and blocks a biological response.

Lock and Key Model

The shape of a drug molecule (key) must fit a specific receptor site (lock) to produce an effect.

Screening Assay

Provides a preliminary indication of the possible presence of a drug.

Confirmation Assay

Provides specific and definitive identification of a particular drug.

Marquis Colorimetric Test

Commonly used to detect Amphetamines/Methamphetamines (color change: orange-red to brown-red to black), and Opiates (color change: purple).

Dillie-Koppanyi Colorimetric Test

Commonly used to detect Barbiturates (color change: violet-blue).

Duquenois-Levine Colorimetric Test

Commonly used to detect Marijuana (color change: purple when reagents are added in sequence).

Scott Test

Commonly used to detect Cocaine (color changes: blue, pink, blue).

Microcrystalline Test

Principle involves formation of unique crystals when a drug reacts with specific reagents, observed under a microscope.

Quantitative Analysis

Provides the amount or concentration of a substance present.

Qualitative Analysis

Provides the identity of the substance(s) present.

Chromatography - Column Function

Contains the stationary phase through which the mobile phase and sample travel.

Chromatography - Stationary Phase

The fixed phase interacting with analytes in the mobile phase.

Chromatography - Mobile Phase

The moving phase that carries the sample through the stationary phase.

Thin Layer Chromatography (TLC)

Separates components of a mixture based on different affinities for stationary and mobile phases.

Retention Factor (Rf)

Calculated by the formula Rf = distance traveled by the solvent front / distance traveled by the compound.

Serology

The study of bodily fluids, especially blood serum, and their reactions.

Forensic Serology

Application of serological techniques in crime investigation involving analysis of bodily fluids.

Serum

Liquid portion of blood after clotting; contains water, proteins, electrolytes, and makes up about 55% of blood.

Red Blood Cells

Transport oxygen and carbon dioxide in the blood.

White Blood Cells

Involved in the immune response, defending against infection.

Platelets

Involved in blood clotting (hemostasis).

Antigens

Molecules on red blood cells stimulating an immune response; determine blood type.

Antibodies

Proteins produced by the immune system that recognize and bind to specific antigens.

A-B-O Blood Typing System - Type A

Contains Antigen A and Antibody B.

A-B-O Blood Typing System - Type B

Contains Antigen B and Antibody A.

A-B-O Blood Typing System - Type AB

Contains both Antigen A and Antigen B; no antibodies.

A-B-O Blood Typing System - Type O

Contains neither Antigen A nor Antigen B; both Antibody A and Antibody B.

Agglutination

Clumping occurs when a blood antigen contacts the matching blood antibody.

Blood Typing in Lab

Adding known antibodies (anti-A serum and anti-B serum) to determine blood type.

US Population Blood Distribution

O (~45%), A (~40%), B (~11%), AB (~4%).

EMIT Technique

Uses antibodies that bind to a drug; presence competes with an enzyme-labeled drug affecting enzyme activity.

Kastle-Meyer Test

A positive result indicates the likely presence of hemoglobin (blood).

Hemastix Test

A positive result indicates the likely presence of hemoglobin (blood).

Luminol

Reacts with iron in hemoglobin producing a glow visible in the dark.

Precipitin Test

Determines if blood is of human origin by reacting antibodies produced in animals with the questioned blood.

Components of DNA

Includes deoxyribose sugar, phosphate group, and a nitrogenous base.

DNA Nucleotide Base Pairing

Adenine pairs with Thymine (A-T) and Guanine pairs with Cytosine (G-C).

Gene

A segment of DNA that contains instructions for building/mantaining an organism; located on chromosomes.

Allele

Different versions of a gene at a chromosome locus (e.g., blue or brown eye color).

Locus

The specific physical location of a gene on a chromosome.

Genotype

The genetic makeup of an individual regarding specific alleles.

Phenotype

Observable characteristics resulting from the interaction of genotype and environment.

Dominant Allele

An allele that expresses its phenotype even with one copy present.

Recessive Allele

An allele that expresses its phenotype only when two copies are present.

Punnett Square

A diagram used to predict possible genotypes and phenotypes in genetic crosses.

Short Tandem Repeat (STR)

Short DNA sequences repeated a variable number of times; e.g., (GATA)n.

STR Genotype Representation

Lists the number of repeats for each allele at a specific STR locus (e.g., 10, 12).

Polymerase Chain Reaction (PCR)

Amplifies a small piece of DNA using cycles of heating and cooling.

Homozygote

An individual with two identical alleles at a specific locus.

Heterozygote

An individual with two different alleles at a specific locus.

Gel Electrophoresis Principle

Separates DNA fragments based on size as they migrate through a gel matrix under an electric field.

CODIS Profile

Combined DNA Index System; a database of DNA profiles that create unique genetic profiles.

Amelogenin

Used to determine a perpetrator's sex based on the lengths of PCR amplified genes on X and Y chromosomes.

Reading CODIS Profile - Green Bars

They represent the amplified DNA fragments (alleles) at specific STR loci.

Reading CODIS Profile - Peaks

Two peaks indicate heterozygous alleles; one peak indicates homozygous alleles.

Reading CODIS Profile - Numbers under Peaks

Represent the number of Short Tandem Repeats (STRs) at specific loci.