Forensic Science: Key Concepts, Cases, and Evidence Analysis

Forensic Science Minor

A degree track offered within the Bachelor of Science in Forensic Science (120 Credit Hours) besides Biology, Chemistry, and Digital Forensics.

Forensis

The literal meaning of the Latin word from which 'forensic' is derived, meaning 'of the market place or forum'.

Forensic Definition

Relating to the application of scientific knowledge to legal problems, belonging to, used in, or suitable to courts of judicature or to public discussion and debate; it can also mean argumentative or rhetorical.

Forensic Disciplines

Trace Evidence, Questioned Documents, Odontology, Pathology, Molecular Genetics, Anthropology, Entomology, Engineering, Firearms/ballistics, Photography, CSI, Psychiatry/Psychology, Digital/Biometrics/Computers, Linguistics, Podiatry, and Accounting.

Will West case

The specific case often associated with the breakdown of the Bertillonage system of identification.

Drug Specimens

Crime laboratories were inundated with these due to accelerated drug abuse in the 1960s.

Optional Services in Crime Labs

Toxicology Unit, Latent Fingerprint Unit, Polygraph Unit, Voiceprint Analysis Unit, or Crime-Scene Investigation Unit.

Kumho Tire Co., Ltd v. Carmichael

The landmark case that determined that the judge acts as a 'gatekeeper' for scientific testimony and any expert testimony.

Medical Personnel Instruction

They should avoid disturbing evidence and approach the victim by an indirect route when they arrive at a crime scene.

Crime Scene Boundaries

The lead investigator must determine the boundaries of the scene and establish the perpetrator's possible path of entry and exit.

Note-Taking Information

Notes must include the identity of the person who contacted the investigator, a personnel log, and the names of personnel present on arrival and those being contacted.

Pixels

The light-sensitive microchip in digital photography that captures light on each tiny picture element.

Overview Photographs

These must include a 'visual tag' to help visually piece the scene together.

Measurement Scales

Scales should be placed as close to the evidence as possible without affecting it in any way.

Computer-Aided Drafting (CAD)

They allow the creation of sketches that are drawn to scale with care and concern for appearance, including three-dimensional finished sketches.

Spiral Search Pattern

The investigator searches in a spiral path from the center to the boundary (outward) or from the boundary to the center (inward).

Packaging Trace Evidence

Ordinary mailing envelopes should be avoided because powders and fine particles will leak out of their corners.

Protective Gear for Evidence Collectors

A face mask and lab coat. Disposable coveralls, shoe covers, and eye protection also offer added precautions.

Mincey v. Arizona

The court determined that a warrant was never issued and the circumstances of the case did not justify a warrantless search (even though it was a homicide scene).

Michigan v. Tyler

Evidence obtained from the initial search was legally seized, but evidence obtained from searches 4, 7, and 24 days later were illegally seized.

Testimonial Evidence

Evidence that is either spoken or written evidence given by a witness under oath.

Hearsay Evidence

Statements made by witnesses who are not present. It is not admissible in court, although it may be relevant in investigations with a less robust burden of proof.

Direct Evidence

The most powerful type of evidence that requires no inference; the evidence alone is the proof (e.g., testimony of a witness who saw an incident first-hand).

Identification of Physical Evidence

The adoption of testing procedures that give characteristic results for specific standard materials.

Sufficient Tests for Identification

The number and type of tests needed must be sufficient to achieve the exclusion of all other substances.

Probability in Evidence Comparison

The frequency of occurrence of an event.

Class Physical Evidence

Forensic scientists must create and update statistical databases for evaluating the significance of class physical evidence.

Evidential Variations

Variations in evidence that can affect its interpretation and significance.

Integrated Ballistic Identification System (IBIS)

Maintained by the ATF, it contains bullet and cartridge casings retrieved from crime scenes and test-fires of guns.

Glass Evidence Reference Database

Contains >700 glass samples.

SICAR

Shoeprint image capture and retrieval.

TreadMark™

Commercial shoeprint product.

Crime-scene reconstruction

Relies on the combined efforts of medical examiners, criminalists, and law enforcement personnel.

Bloodstain Pattern Analysis (BPA)

Relies upon Physics (Fluid Dynamics), Mathematics (Geometry, Trigonometry), and Biology (Serology testing, DNA).

Angle of Impact ($\Theta$)

Calculated using the equation: $\sin \Theta$ = width of stain / length of stain.

Static Transfers

Involve no lateral motion between the objects (e.g., foot/handprints).

Dynamic Transfers

Involve lateral motion (e.g., swipes or wipes).

Swipe Pattern

A bloodstain resulting from a blood-covered object depositing blood on a surface (relative motion occurs).

Wipe Pattern

An altered bloodstain pattern resulting from an object moving through a preexisting wet bloodstain, thus removing blood.

Spatter stains

Created by an external force applied to a source of liquid blood.

Projected Pattern

Created when a victim suffers an injury to a main artery or the heart, distinguished by the oxygenated blood spurting from the artery, which tends to be a brighter red color.

Expirated Pattern

Differentiated from other spatter patterns by the presence of bubbles of oxygen in the drying drops or a lighter color due to dilution by saliva.

Pool of blood

Occurs when blood collects in a level and undisturbed place; its drying time can yield information about the timing of events that accompanied the incident.

Artifacts in BPA

Bloodstains that are not formed as a result of the incident but produced by an external action either before or after the incident.

Leuco-crystal Violet

Presumptive chemical test for blood that changes from colorless to blue/violet.

Luminol

Presumptive chemical test for blood that changes from colorless to blue chemiluminescence.

Kastle-Meyer

Presumptive chemical test for blood that changes from colorless to pink.

Leuco-malachite Green

Presumptive chemical test for blood that changes from colorless to green.

Amido Black

Dark Blue Dye Protein Stain used as a presumptive chemical test for blood.