Forensic Science: Bloodstain Pattern Analysis, Death Investigation, and Toxicology

Comprehensive vocabulary flashcards covering Bloodstain Pattern Analysis (BPA), Medicolegal Investigation of Death, and Forensic Toxicology based on the lecture study guide.

Bloodstain Pattern Analysis (BPA)

The study of the size, shape, and distribution of bloodstains to reconstruct events at a crime scene, such as the force involved, victim position, and sequence of events.

Surface Tension (Blood)

The physical property that causes blood to behave as a fluid with predictable cohesion, causing a falling blood drop to form a sphere in mid-air.

Smooth Surfaces (Bloodstain Impact)

Target surfaces that preserve blood droplet shape upon impact, producing stains with clean, rounded edges.

Rough/Porous Surfaces (Bloodstain Impact)

Target surfaces that disrupt blood droplet integrity upon impact, resulting in irregular scalloped edges and satellite spatter.

Passive Stains

Bloodstain patterns formed primarily by gravity acting on a relatively still blood source, including drops, pools, and flows.

Projected Stains

Bloodstain patterns formed when an external force or energy is applied to a blood source, such as impact spatter, cast-off from swung objects, or arterial spray.

Transfer Stains

Bloodstain patterns created when a wet, bloody surface comes into contact with another surface, including shoe prints, handprints, swipes, and wipes.

Directionality (Bloodstain)

The characteristic indicating flight path, determined because the elongated tail of a bloodstain always points in the direction the drop was traveling when it impacted the surface.

Angle of Impact Formula

The mathematical calculation used to determine impact angle: $\sin(\alpha) = \frac{\text{Width}}{\text{Length}}$ or $\alpha = \arcsin\left(\frac{\text{Width}}{\text{Length}}\right)$, where width is the smaller measurement and length excludes the tail.

Region of Convergence

The two-dimensional ($2\text{D}$) point on a surface where directional lines drawn through individual bloodstains intersect.

Dr. Sam Sheppard Case (1954/1966)

A landmark case where the re-examination of bloodstain patterns by Dr. Paul Kirk overturned a wrongful murder conviction, demonstrating the necessity of standardized, objective BPA methodology.

Medical Examiner (ME)

An appointed licensed physician, typically board-certified in forensic pathology, who investigates suspicious deaths and directly performs autopsies based on medical qualifications.

Coroner

An elected death investigation official rooted in historic English tradition who may or may not be a physician, often relying on contracted forensic pathologists to perform autopsies.

Cause of Death (COD)

The specific injury or disease that initiates the lethal chain of physiological events leading to death (e.g., a gunshot wound to the torso).

Mechanism of Death

The specific physiological or biochemical disruption produced by the cause of death (e.g., massive hemorrhage or fatal cardiac arrhythmia).

Manner of Death (MOD)

The broad legal classification of circumstances surrounding death, categorized under NASH + Undetermined: Natural, Accident, Suicide, Homicide, or Undetermined.

Algor Mortis

The postmortem cooling of the body toward ambient temperature, declining at an approximate rate of $\sim 1.5^\circ\text{C}$ per hour for the first $8$ hours.

Livor Mortis

The postmortem settling and pooling of blood in dependent (lowest) regions of the body due to gravity, becoming visible around $1$ hour post-mortem.

Rigor Mortis

The postmortem chemical stiffening of muscles that occurs after circulation ceases, reaching peak rigidity around $12$ hours post-mortem.

Sharp Force Trauma

Trauma resulting in incised wounds with clean, smooth edges, typically caused by cutting or stabbing instruments.

Blunt Force Trauma

Trauma resulting in lacerations characterized by rough, torn tissue edges and tissue bridging fibers.

Song Ci (1247 CE)

Historical author of 'The Washing Away of Wrongs', an early treatise that established systematic, empirical observation in death investigation.

Forensic Toxicology

The study of drugs, poisons, alcohol, and other chemicals affecting the human body within legal and medicolegal contexts.

Paracelsus's Principle

The foundational toxicological concept stating that 'The dose makes the poison,' meaning any chemical substance can cause toxicity if administered at a sufficiently high dose.

Xenobiotics

Foreign chemical substances present within an organism that are not naturally produced or expected to be found in the human body.

ED50

The effective dose that produces a specific therapeutic or pharmacological effect in $50\%$ of a tested population.

LD50

The individual dose required to be lethal to $50\%$ of a tested population, quantified in $\text{mg/kg}$ of body weight.

ADME Processes

The four fundamental pharmacokinetic stages of a drug: Absorption (entry into bloodstream), Distribution (transport to tissues), Metabolism (biochemical breakdown), and Excretion (elimination from the body).

First-Pass Metabolism

The hepatic processing where an orally ingested drug travels via the portal system directly to the liver, significantly metabolizing the active compound and reducing systemic bioavailability before reaching general circulation.

Immunoassays (Screening Tests)

Rapid preliminary analytical tests relying on antigen-antibody reactions that provide high sensitivity but carry a risk of cross-reactivity.

Confirmatory Tests (GC-MS / LC-MS)

Definitive analytical techniques, such as Gas Chromatography–Mass Spectrometry, that separate and break molecules into unique mass fragments to provide unambiguous identification.

Henry's Law (Alcohol Analysis)

The physical law relating breath alcohol concentration (BrAC) to blood alcohol concentration (BAC), establishing a biological ratio where BAC is approximately $2{,}100$ times greater than BrAC ($2100:1$).

Postmortem Redistribution

The phenomenon occurring after death where drugs diffuse from concentrated tissue stores into central blood vessels; it necessitates sampling peripheral sites (such as femoral blood) for accurate toxicology interpretation.