FORS Quiz 1: Bold Terms Glossary (Chapters 1–6)

Comprehensive vocabulary flashcards covering the key boldface terms across Chapters 1 through 6 and the chapter body appendix from Houck & Siegel's Fundamentals of Forensic Science (3rd Ed.).

Forensic science

The science of associating people, places, and things involved in criminal activities; these disciplines assist in investigating and adjudicating criminal and civil cases.

Criminalistics

The branch of forensic science that involves the collection and analysis of physical evidence generated by criminal activity; sometimes used synonymously with forensic science (from German kriminalistik).

Criminalists

What forensic scientists are called in some forensic science laboratories.

American Society of Crime Laboratory Directors (ASCLD)

Professional association of crime laboratory directors.

ASCLD Laboratory Accreditation Board (ASCLD-LAB)

The laboratory accreditation board of ASCLD.

Behavioral sciences

Area of forensic science covering the behavioral/psychological disciplines applied to criminal investigation.

Forensic anthropology

Area of forensic science applying anthropology, especially skeletal analysis, to legal cases.

Forensic engineering

Area of forensic science applying engineering to failures/accidents in legal cases.

Forensic odontology

Area of forensic science applying dentistry (e.g., dental identification, bite marks) to legal cases.

Forensic pathology

Area of forensic science covering the medical determination of cause and manner of death.

International Organization for Standardization (ISO)

In the U.S., the standard for laboratory accreditation is ISO 17025, "General requirements for the competence of testing and calibration laboratories."

Questioned documents

Area of forensic science examining documents whose source or authenticity is disputed.

Toxicology

Area of forensic science covering the study/detection of drugs and poisons and their effects.

American Society for Testing and Materials, International (ASTM)

Publishes voluntary consensus standards for many sciences, including forensic science (Committee E30); "voluntary" because individuals and agencies independently choose to follow them.

Forensic Science Education Programs Accreditation Commission (FEPAC)

Commission initiated by the American Academy of Forensic Sciences (AAFS) that maintains and enhances the quality of forensic science education by formally evaluating and recognizing 4-year, college-level academic programs.

Technical Working Group on Education and Training in Forensic Science (TWGED)

A working group sponsored by the National Institute of Justice that developed guidelines for forensic science education and training.

Chain of custody

The documentation of who had what items of evidence and when, from the smallest fiber to an entire car; it begins at the crime scene when the evidence is collected.

Crime scene investigator (CSI)

The trained personnel who process a crime scene; SOPs/protocols guide the CSI for comprehensive and accurate evidence collection, documentation, and transmittal to the laboratory.

Context

The relationships/positions of items at a scene relative to each other and their surroundings, which must be documented before processing destroys them.

Datum

A fixed reference point for all three-dimensional measurements (e.g., something permanent such as a light switch corner, a tree, or a post).

Artifact

A human-made or modified portable object.

Feature

A non-portable artifact, such as a fire pit, a house, or a garden.

Organic or environmental remains

Natural remnants ("non-artifactual") that nonetheless indicate human activity, such as animal bones or plant remains, and also soils and sediments.

Provenance

The origin and derivation of an item in three-dimensional space, in relation to a datum and other items.

Bloodborne pathogens (BBPs)

Disease-causing microorganisms in blood and other body fluids (such as AIDS and hepatitis) that pose an infection risk at crime scenes.

Universal precautions

The primary OSHA concept for infection control: treating all human blood and other potentially infectious materials as if infectious (barrier protection, gloves, eye/face protection, sharps handling, decontamination).

Material safety data sheet (MSDS)

Provides information on the hazards of a particular material so workers can handle it safely.

Trier of fact

Whoever determines guilt or innocence (the judge or the jury).

Evidence

Information — testimony, documents, or material objects — given in a legal investigation to make a fact or proposition more or less likely.

Demonstrative evidence

Items created to augment or explain real evidence; not generated by the incident itself, but used to help the trier of fact understand the evidence or circumstances.

Proxy data

Not the transfer itself, but the remnants of it; science uses proxy data to represent past events.

Direct transfer

Evidence transferred from a source to a location with no intermediaries (source A to recipient B).

Indirect transfer

Transfer of evidence through an intermediary (e.g., dog hairs reaching an office chair the dogs never sat in).

Locard exchange principle

"When two things come into contact, information is exchanged" (Locard, 1930); the core principle of forensic science.

Persistence

Once evidence transfers, it remains until removed/degraded; how long depends on the evidence, its location, the environment, time since transfer, and activity around the location.

Contamination

Transfers that occur after the crime-related activity has stopped.

Identification

Examining the chemical and physical properties of an object and using them to classify it into successively smaller classes.

Class

A group of things with similar characteristics; the size of the class can vary, and the definition is "movable" — it depends on the characteristics chosen.

Common source

If two objects share a class identity, that may indicate they come from a common source.

Individualization

Classifying an object into a group with only one member (itself); occurs when at least one unique characteristic is found in both the known and the questioned item.

Questioned evidence

Evidence whose original source is unknown (e.g., paint on the victim's coat); compared with objects whose source is known.

Known evidence

Evidence whose source is known (e.g., paint taken from the suspect's car).

Coincidental associations

Two things that appear associated purely by chance; coincidental matches are extremely rare.

Comparison

One of the fundamental processes of evidence analysis: comparing questioned evidence against controls/knowns — materials whose source is known, used for comparison with unknown evidence.

Positive control

A control material expected to give a positive test result (e.g., known blood).

Negative control

A control material expected to give a negative test result; controls are materials whose source is known, used for comparison with unknown evidence.

False positive (Type I error)

Concluding a substance is present when it is not (a negative control not being used can cause it); serious because it can falsely incriminate a person.

False negative (Type II error)

Concluding a substance/condition is absent when it is present (failure to run a positive control can cause it); can falsely exonerate someone who committed the crime.

Scientific method

The process of science: a systematic way of examining the world and learning about it through observation, hypotheses, and testing.

Testability

The first hallmark of science: the questions asked must be testable; untestable questions are not scientific.

Repeatability

The second hallmark of science: science is a public endeavor and its results must be repeatable/reproducible by others.

Hypotheses

In the language of science, the particular questions to be tested.

Probative value

The ability of evidence to prove or disprove a point in issue.

Simple magnification system

Magnification with a single lens, e.g., a pocket magnifier or hand lens; practical limit about $10\times$ to $15\times$.

Compound magnification system

Magnification in two stages (objective, then eyepiece); total magnification is the product of the two stages.

Virtual image

An image that does not exist where it appears to be (e.g., a mirror image) and cannot be caught on a screen; visible only as a result of the magnification system.

Real image

An image that actually exists where it appears and can be caught on a screen (contrast virtual image).

Focal length

The distance from the two focal points ($F_1$ and $F_2$) of a lens; determines much of the image quality.

Resolution

The minimum distance two objects can be separated and still be seen as two objects (about $0.1\,\text{mm}$ for the human eye at $25\,\text{cm}$).

Empty magnification

An increase in magnification without an increase in resolution.

Eyepiece

The lens (ocular) at the top of the microscope that the observer looks into.

Monocular

Having a single eyepiece/viewing tube (contrast binocular, two).

Field of view

The area of the specimen visible through the microscope at a given magnification.

Objective

The lens closest to the object or specimen being viewed; common magnifications are $4\times$, $10\times$, $15\times$, $20\times$, and $25\times$.

Numerical aperture

An angular measure of a lens's light-gathering ability; $NA = n \cdot \sin(\theta)$, and the minimum resolvable distance $d = \frac{\text{wavelength}}{2 \cdot NA}$.

Tube length

The distance from the lowest part of the objective to the upper edge of the eyepiece tube; $160\,\text{mm}$ is standard in modern microscopes (some objectives are marked "170 mm").

Coverslips

Thin glass plates placed over a specimen on a slide; the recommended coverslip thickness marked on objectives is $0.17\,\text{mm}$.

Chromatic aberration

A lens defect in which different colors/wavelengths are not brought to the same focus; achromatic objectives are corrected to reduce it.

Curvature of field

The aberration in which a flat specimen is focused onto a curved surface, so the whole field cannot be in focus at once; plan objectives correct for it.

Plan achromats

Objectives corrected for chromatic aberration (achromat) and for curvature of field to give a flat field (plan).

Spherical aberration

Distortion that results from a lens not being properly spherical.

Fluorites

Objectives a step up in correction from achromats, so called because the mineral fluorite is used in making them; also called semi-apochromats.

Semi-apochromats

The same corrected objectives as fluorites.

Infinity-corrected lens systems

Systems in which the image distance is set to infinity and a lens within the tube forms the image; objectives are marked "$\infty$".

Focus

The point/position at which the image is sharp and clear.

Mechanical stage

The specimen platform fitted with mechanical controls to move the specimen precisely.

Rotating stage

A microscope stage that rotates the specimen, used in polarized light microscopy to turn an anisotropic specimen between crossed polarizers.

Condenser

The lens system used to obtain a bright, even field of view and improve image resolution.

Condenser diaphragm

The adjustable diaphragm in the condenser that controls the cone/aperture of light delivered to the specimen.

Field diaphragm

The diaphragm that controls the diameter/size of the illuminated field of view.

Critical illumination

Illumination that concentrates the light on the specimen; highlights edges but may be uneven.

Köhler illumination

Illumination (August Köhler, 1893) that sets the light rays parallel throughout so they evenly illuminate the specimen; the standard setup.

Snell's Law

The refraction law $N_1 \sin(\theta_1) = N_2 \sin(\theta_2)$ relating the refractive indices ($N$) of two materials and the angles ($\theta$) of incidence and refraction; if the two indices are equal, light passes through without refraction.

Mounting media

The materials in which samples are mounted; samples viewed in transmitted light must be in a material with a refractive index close to their own.

Mountants

Materials used to mount a specimen for microscopic viewing (mounting media).

Polarizing light microscope

A microscope using two polarizing filters (polarizer and analyzer) to examine specimens in plane-polarized light or under crossed polars; one of the most powerful tools forensic scientists have.

Isotropic

Having the same optical properties in all directions.

Polarizer

One of the two polarizing filters ("polars") in a PLM, set below the specimen with its preferred vibration direction left-to-right ("east–west").

Polarization colors

The colors produced when out-of-phase light waves from an anisotropic specimen strike the analyzer and are diffracted into various colors depending on retardation; read against the Michel-Lévy chart.

Fluorescence

The luminescence of a substance excited by radiation.

Phosphorescence

Luminescence that continues after the exciting radiation stops.

Fluorophores

The fluorescing substances/molecules in a specimen that emit light when excited.

Electromagnetic radiation

Various forms of energy in the form of waves; can also be thought of as tiny packets of energy called photons.

UV/visible light

Ultraviolet light (about $200$ to $450\,\text{nm}$) and visible light (about $450$ to $750\,\text{nm}$); a photon in this region causes electron promotion in atoms and molecules.

Infrared light

The region of the electromagnetic spectrum just below red visible light ("infra" = below); absorbed by all molecules and causes the bonds holding atoms together to vibrate and/or rotate.

Wavelength

The distance between corresponding points (peaks) of a wave ($\lambda$), expressed in units of length such as nanometers.

Frequency

The number of cycles per second of a wave ($\nu$), measured in Hertz; related to wavelength by $c = \lambda\nu$, so as frequency increases, wavelength decreases.

Wavenumber

The reciprocal of the wavelength (with the wavelength expressed in cm), giving a value in $\text{cm}^{-1}$; a way of expressing frequency.

Photon

A tiny packet of energy ($E$) of electromagnetic radiation; $E = h\nu$, where $h$ is Planck's constant.

Spectrum

A record/plot of light intensity against wavelength; the exact wavelengths a material absorbs are characteristic of it.