IAI SP4 flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Datum point

A fixed, permanent reference point at a scene from which all measurements are taken; the sketch must state its location, the units used, and the compass orientation.

Triangulation measurement

A scene measurement method that locates an item by measuring distances from two known fixed reference points, forming a triangle whose intersection fixes the item's position.

Zone search pattern

A search method that divides a large or multi-room scene into quadrants or zones, with each searcher assigned a zone so that no area is missed or searched twice.

Locard's exchange principle

The principle that every contact between two objects leaves a trace of one on the other, justifying collection of contact surfaces between suspect, victim, and scene.

Rough sketch

The first working drawing made at the scene, showing items, measurements, and reference points; it is later used to produce the finished scale diagram.

Overall photograph

A wide photograph that establishes the scene and its context, showing the relationship of the area to its surroundings before any item is moved or collected.

Depth of field

The range of distance in a photograph that appears acceptably sharp; it increases with a smaller aperture and shorter focal length and decreases at close subject distances.

Oblique lighting

Light directed at a low angle across a surface to reveal texture, indented writing, or impression detail that would be invisible under direct or axial illumination.

Photogrammetry

A method of deriving measurements from photographs taken with a known scale and calibrated camera position; it requires documented calibration and stated error margins.

Alternate light source

A high-intensity light such as UV, IR, or a laser used with barrier filters to make body fluids, fibers, or treated latent prints fluoresce or absorb visibly.

Cyanoacrylate fuming

A latent print development method in which cyanoacrylate vapor polymerizes on print residue on non-porous surfaces, producing a white deposit later stained for contrast.

Ninhydrin

A chemical reagent that reacts with amino acids in latent print residue on porous surfaces such as paper, producing a purple product; heat and humidity accelerate the reaction.

Physical developer

A silver-based reagent used on porous surfaces, including paper that has been wet, to develop latent prints after amino-acid reagents such as ninhydrin have been applied.

ACE-V

The comparison framework: Analysis of each print, Comparison side by side, Evaluation of agreement or exclusion, and independent Verification by a second qualified examiner.

Level 2 detail

Friction ridge features including ridge endings, bifurcations, dots, islands, and spurs; their type, position, and relationship form the basis of a comparison.

Electrostatic lifting

A method that lifts dry footwear or tire residue from a surface using a charged film, preserving the pattern for photography and comparison without disturbing the material.

Chain of custody

A chronological record of every transfer of an item, including collector, date, time, location, recipient, and purpose; a break can reduce or destroy admissibility.

Paper packaging rule

Biological and moist items are packaged in paper so they can dry and breathe; plastic traps moisture and promotes degradation and is reserved for dry non-biological items.

Evidence seal

Evidence tape placed across a package opening with the sealer's initials, date, and time written over it, so that any later opening is visibly detectable.

Puncture-resistant container

Rigid packaging required for needles, blades, and broken glass to prevent injury and loss; it is labeled as a sharps hazard and sealed like other evidence.

Universal precautions

The practice of treating all biological material as potentially infectious, using gloves, eye protection, and masks and changing gloves between items and surfaces.

Angle of impact formula

For a bloodstain, the impact angle is calculated as sin θ = width divided by length of the stain; the result is used to back-project the point of origin.

Control sample

A known reference sample collected from the victim, suspect, or scene, packaged separately, against which a questioned trace or biological sample is compared.

Gunshot residue stub

An adhesive collection stub applied to the hands to collect primer residue; it is time-sensitive and must be labeled with collection time and the person's recent activities.

Hair root sheath

Follicular tissue attached to a pulled hair, distinguishing it from a shed telogen hair; the sheath indicates forceful removal and may yield nuclear DNA.

Henry classification

A tenprint classification system that forms a primary fraction from the presence of whorl patterns in paired fingers, used to file and retrieve print records.

Loop pattern

A fingerprint pattern with one delta and one core in which ridges enter one side and exit the same side; it is classified as ulnar or radial by the delta direction.

Whorl pattern

A fingerprint pattern containing at least two deltas, with subtypes plain, central pocket, double loop, and accidental; whorls raise the Henry primary classification value.

Ridge count

The number of ridges crossed by a straight line drawn from the delta to the core of a loop, used in classification and comparison documentation.

Daubert standard

A federal admissibility test weighing testability, peer review, known error rate, controlling standards, and general acceptance; the judge decides admissibility, the jury decides weight.

Linear sequential unmasking

A bias-control procedure in which the examiner analyzes and documents the unknown print before seeing reference prints or case context, reducing contextual influence on the conclusion.

ISO/IEC 17025

The international standard for competence of testing and calibration laboratories; forensic laboratories seek accreditation to it and are audited and proficiency-tested against its requirements.