FORENSIC SCIENCE HOSA STUDY GUIDE (2025-2026)

Forensic Science

Application of scientific principles to matters of law.

Song Ci

First documentation of forensic medicine in 1248 CE.

Lancaster Case

First conviction based on physical evidence in 1784.

Marsh Test

Detection of arsenic in poisoning developed in the 1850s.

Francis Galton

Developed the fingerprint classification system in 1892.

Edmond Locard

Established the world's first forensic lab in Lyon, France in 1910.

Locard's Exchange Principle

Every contact leaves a trace.

FBI Crime Lab

Created in 1932.

Major Branches of Forensic Science

Pathology, Anthropology, Toxicology, Entomology, Odontology, Serology, DNA Analysis.

Crime Scene Investigator (CSI)

A professional who investigates crime scenes.

Forensic Pathologist

A medical doctor who determines the cause of death.

Chain of Custody

The process of maintaining and documenting the handling of evidence.

Physical Evidence

Tangible items such as weapons, fibers, and hair.

Biological Evidence

Includes DNA, blood, and saliva.

Class Evidence

Narrows to a group, such as blood type.

Individual Evidence

Unique to one source, such as DNA or fingerprints.

Manner of Death

Categories include natural, accidental, suicidal, homicidal, and undetermined.

Cause of Death

The injury or disease responsible for death.

Mechanism of Death

The physiological process leading to death, e.g., exsanguination.

Algor Mortis

Cooling of the body at approximately 1-1.5°F/hour.

Livor Mortis

Blood pooling that begins 2 hours after death.

Rigor Mortis

Muscle stiffening that begins 2-12 hours after death.

Toxicology

The study of the effects of chemicals, drugs, and poisons on the body.

Presumptive Tests

Quick, inexpensive tests such as color tests.

Confirmatory Tests

Tests such as Gas Chromatography-Mass Spectrometry (GC-MS).

Pharmacokinetics

The process of absorption, distribution, metabolism, and excretion (ADME) of drugs.

Kastle-Meyer test

A presumptive test for blood that turns pink if hemoglobin is present.

Luminol

A chemical that reacts with iron in blood to produce a blue glow.

Takayama crystal test

A confirmatory test for blood.

DNA typing

A method used to identify individuals based on their unique DNA profiles.

Passive bloodstains

Bloodstains that are gravity-driven, such as drops and pools.

Transfer bloodstains

Bloodstains resulting from contact between surfaces.

Projected bloodstains

Bloodstains created from applied force, such as arterial spurts or cast-off.

DNA

Deoxyribonucleic acid, a molecule that carries genetic information.

STR analysis

Short Tandem Repeats analysis, a standard forensic method used in CODIS.

Mitochondrial DNA

DNA that is inherited maternally and useful in analyzing degraded samples.

PCR

Polymerase Chain Reaction, a technique used to amplify DNA fragments.

Gel Electrophoresis

A method for separating DNA fragments by size.

Restriction Enzymes

Enzymes that cut DNA at specific sequences.

CODIS

Combined DNA Index System, a database maintained by the FBI.

Forensic Psychology

The application of psychology to legal issues.

Competency

The mental capacity of a defendant during a trial.

Insanity

The mental state of a defendant at the time of committing a crime, as defined by the McNaughten Rule.

Malingering

The act of faking illness for external gain.

Psychopathy

A personality disorder characterized by a lack of empathy and manipulative behavior.

Sociopathy

A personality disorder similar to psychopathy, often associated with environmental factors.

Forensic Psychiatry

The branch of psychiatry that evaluates sanity, risk assessment, and mental health treatment.

Criminal profiling

The analysis of behavioral patterns to predict traits of offenders.

Haversian canal

The microscopic structure that identifies human bone.

Blowflies

Typically the first insects to arrive because they are attracted to moist openings and wounds.

PMI estimation

The most accurate estimation uses larval stage development.

Blowfly life cycle order

Egg → Larva → Pupa → Adult.

Insect colonization delay

Delayed by burial.

Study of insect evidence

Important primarily for estimating PMI.

Blood type analysis

Considered class evidence.

Takayama test

Produces hemochromogen crystals.

Angle of impact of a blood droplet

Determined by shape.

STR

Stands for Short Tandem Repeat.

McNaughten Rule

Relates to the insanity defense.

Forensic psychiatrists

Mainly assess mental competency.

Psychopaths

Characterized by manipulative, remorseless behavior.

Competency evaluation

Determines sanity at time of trial.

Individual identification evidence

Blood type can never provide this.

Metabolism phase

A drug metabolized by the liver indicates this phase of pharmacokinetics.

Third instar larva

Provides the most precise time of colonization.

Facial approximation

The use of skull features to reconstruct facial appearance.

DNA profiling

Uses base-pair comparison.

FBI's main forensic laboratory

Located in Quantico.

Transient evidence

Odor is considered this type of evidence.

First responder's primary duty

Secure safety and preserve evidence.

Precipitin test

Confirms blood's human origin.