IAI SP5 flashcards

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

Angle of impact formula

The impact angle of a bloodstain is derived from sin θ = width divided by length of the elliptical stain, where width is the minor axis and length the major axis.

Point of convergence

The two-dimensional point where lines drawn through the long axes of individual bloodstains intersect, indicating the area where the blood source was located.

Cast-off pattern

A linear trail of bloodstains produced when blood is flung from a moving object such as a weapon, with stain spacing reflecting the swing arc and speed.

Void pattern

An area free of bloodstains surrounded by stained surfaces, indicating that an object or person occupied that space when blood was deposited.

Expirated blood

Blood forced from the nose or mouth by air pressure, appearing as fine mist with air bubbles and mucus, often near a victim's face.

Transfer stain

A bloodstain created when a bloody object contacts a surface, often reproducing the object's shape or fabric weave pattern.

Chain of custody

A documented record of every transfer and handler of evidence from collection through analysis and court, ensuring integrity and admissibility.

Grid search pattern

A scene search method in which parallel lines are walked in one direction, then repeated perpendicularly to ensure complete coverage of the area.

Datum point

A fixed reference point in a crime scene sketch from which measurements to evidence are taken, ensuring accurate reconstruction of locations.

Transient evidence

Evidence that is perishable or easily altered, such as odors, temperature, or footprints in snow, requiring immediate documentation before it is lost.

Packaging biological evidence

Biological evidence should be air-dried and placed in paper packaging; sealing wet items in plastic promotes mold and DNA degradation.

Latent footwear impression

An invisible footwear print, often in dust or residue, that requires enhancement such as powder or electrostatic lifting to be visualized.

Dental stone casting

A method for preserving three-dimensional footwear impressions in soil or snow by pouring mixed dental stone into the impression and allowing it to harden.

Class characteristics footwear

Features shared by a group of shoes, such as tread pattern and size, used to narrow a source to a brand or model.

Individual characteristics footwear

Unique features of a specific shoe, including wear patterns, cuts, and embedded debris, that may permit attribution to a single source.

Electrostatic dust lifter

A device that applies a static charge to lift dry dust footwear impressions from hard surfaces onto a film for preservation and examination.

Composite drawing

A facial image constructed from a witness's description using feature-by-feature interview techniques and standardized reference charts.

Age progression

A forensic art technique that modifies a photograph to estimate how a person's face may change over time due to aging and lifestyle factors.

Tissue depth markers

Small pegs placed at facial landmarks on a skull to indicate average tissue thickness, guiding two- or three-dimensional facial reconstruction.

Demonstrative evidence

Visual aids such as diagrams or models used in court to illustrate testimony; they must be accurate and not unfairly prejudicial.

Photographic triad

The three exposure controls: aperture (depth of field), shutter speed (motion), and ISO (sensitivity and noise), balanced for a proper exposure.

ABFO No. 2 scale

A forensic reference scale with right-angle markings used in evidence photographs to document size and correct for perspective distortion.

Oblique lighting

A lighting technique in which light strikes a surface at a low angle to reveal texture and detail, useful for impressions and tool marks.

Depth of field

The range of distance in a photograph that appears acceptably sharp; it increases with smaller apertures and shorter focal lengths.

Original file preservation

Forensic image handling requires preserving the unaltered original file, hashing it, and documenting all enhancement steps on working copies.

Frame rate calculation

Knowing a camera's frames per second allows analysts to compute the time interval between events by counting frames and dividing by the rate.

Video hash value

A cryptographic checksum of a video file used to verify that the evidence has not been altered since acquisition.

Camera calibration video

The process of determining a camera's parameters, such as lens distortion and position, so measurements from video can be reliable.

ACE-V method

The standard latent print methodology: Analysis, Comparison, Evaluation, and Verification, with the final step performed by a second examiner.

Cyanoacrylate fuming

A development technique in which superglue vapor polymerizes on latent print residue on non-porous surfaces, making the print visible for powdering or dye staining.

Ninhydrin development

A reagent that reacts with amino acids in sweat to produce a purple color, used to develop latent prints on porous surfaces such as paper.

Henry classification

A tenprint filing system that groups records by fingerprint pattern types and ridge counts to enable manual searching of large collections.