Intro to Forensics

Unit 3 Exam

Latent print

An invisible impression formed by natural sebum and perspiration transferred onto a surface, requiring optical, physical, or chemical processing for visualization.

Patent print

A visible friction ridge impression transferred directly onto a substrate by a foreign medium such as blood, ink, paint, or grease.

Plastic print

A three-dimensional impression impressed into a malleable, soft material such as wax, putty, or fresh paint.

Most frequently encountered friction ridge impression at crime scenes

Latent print

Premise of friction ridge individualization

The forensic principle that permanent dermal structures combined with absolute biological uniqueness permit positive source attribution.

Galton detail threshold for friction ridge identification

There is no fixed minimum number of features mandated; identification depends on the qualitative and quantitative assessment of the examiner.

Reason identical twins do not share identical friction ridge impressions

Ridge formation is influenced by non-genetic intrauterine environmental variables, such as differential pressure from amniotic fluid and contact within the womb.

Three main friction ridge pattern classes and relative frequencies

Loops ($65\%$), whorls ($30\%$), and arches ($5\%$).

ACE-V methodology

A systematic forensic examination process consisting of Analysis (assessing the unknown and known exemplar), Comparison, Evaluation (source determination), and Verification.

Level 1 detail in friction ridge examination

Overall ridge flow, orientation, pattern classification, core, delta placement, and ridge counts; sufficient only to determine exclusions or inconclusive findings.

Level 2 detail in friction ridge examination

Specific Galton details (minutiae), such as bifurcations, ending ridges, dots, and continuous ridge relationships; capable of supporting identification or exclusion.

Level 3 detail in friction ridge examination

Microscopic dimensional structures, including pore morphology, exact edge contours, and individual ridge widths; capable of supporting identification or exclusion.

Verification phase requirement in latent print analysis

An independent re-examination conducted by a separate qualified examiner, mandatory for all positive source identifications.

Firearm

Any weapon designed to, or that may be readily converted to, discharge a projectile by the combustion of an explosive propellant.

Rifling

Helical grooves cut or formed along the interior bore of a firearm barrel to impart gyroscopic rotational spin to a projectile, stabilizing trajectory and accuracy.

Comparison microscope

An optical instrument featuring two compound microscopes joined by an optical bridge, enabling side-by-side microscopic comparison of two specimens simultaneously.

Class characteristics examined on fired cartridge cases

Caliber designation, breech face marking style, firing pin shape, and extractor/ejector positional marks.

Class characteristics examined on fired bullets

Caliber, count of land and groove impressions, direction of rifling twist, and physical widths of lands and grooves.

Source of individual characteristics on firearms evidence

Random microscopic imperfections and striations transferred to bullets and cartridge cases from unique tool-working marks on the barrel and breech mechanism.

Presumptive drug test

A rapid qualitative screening procedure, often relying on chemical color change, that suggests the possible presence of a drug class but requires confirmatory analysis.

Marquis reagent

A screening color-test reagent used to presumptively detect the presence of alkaloids and opiate compounds.

Gas Chromatography-Mass Spectrometry (GC-MS)

A two-phase analytical method that separates volatile mixtures and identifies individual molecular compounds by their fragmentation spectra, serving as the gold standard for confirmation.

Microspectrophotometry

An analytical technique coupling visible or ultraviolet light spectroscopy with microscopy, used to distinguish non-destructive spectral profiles of trace inks and dyes.

Time constraint for gunshot residue (GSR) sampling

Approximately $4\text{ hours}$ post-discharge, after which microparticles typically detach through physical movement, transfer, or washing.

Condition required to identify a severed piece of tape to a parent roll

A physical fracture match aligning microscopic surface striations and irregularities across torn ends.

Forensic toxicology

The quantitative and qualitative determination of foreign drugs, poisons, and their metabolic byproducts within biological fluids and post-mortem tissues.

Mathieu Orfila

The nineteenth-century scientist recognized as the father of forensic toxicology for authoring the first systematic classification of poisons and proving that toxic agents must undergo bodily absorption to exert systemic effects.

Biological specimens analyzed during post-mortem toxicological screening

Heart and peripheral blood, urine, liver tissue, and vitreous humor.

Scent associated with cyanide toxicity

A subtle odor resembling bitter almonds, an intoxication often clinically misidentified as an acute asthmatic event or myocardial infarction.

Thallium

A highly toxic metallic byproduct of heavy metal smelting that was historically utilized as a commercial rodenticide and pesticide before domestic restrictions.

Ricin

A lethal ribosome-inactivating protein extracted from castor beans (Ricinus communis) whose most lethal exposure routes include inhalation and parenteral injection.

Statutory blood alcohol concentration (BAC) limit for vehicle operation

$0.08\,\text{g/dL}$ (or $0.08\%$).