IAI SP9 key terms

The acute angle between a blood drop's flight path and the target surface, calculated from the drop's width-to-length ratio; it determines how elliptical the resulting stain appears.

The two-dimensional region on a surface where lines drawn through the long axes of related bloodstains intersect, indicating the horizontal position of the blood source.

The three-dimensional location in space from which blood was projected, estimated by combining convergence geometry with impact angles and the resulting height or distance calculation.

A linear trail of bloodstains flung from a blood-bearing object such as a weapon during a swinging motion; the trail's direction and spacing help infer the number and location of swings.

Blood dispersed when a force strikes a wet bloody surface, producing a spray of droplets whose size generally decreases as the energy applied to the source increases.

Small secondary droplets that separate from a parent drop when it strikes a surface, landing around the parent stain and often indicating the drop's direction of travel.

A bloodstain elongated in the direction of travel because the drop struck the surface at an oblique angle; its shape is used to derive impact angle and directionality.

The compass orientation, measured on the target surface, toward which a blood drop was traveling; it is read from the tapered end of an elongated stain and used to draw convergence lines.

A documentation and reconstruction technique in which strings or rods are anchored at individual stains and aligned with their trajectories to visualize the three-dimensional area of origin.

An absence of bloodstaining in an otherwise stained area, caused by an intervening object that was later moved; it can suggest the shape and former position of that object.

A bloodstain created when a wet, bloody object or surface contacts a clean surface, reproducing the contact shape or a smeared, directional impression of it.

The chronological written record of who collected, handled, transferred, and stored each item of evidence, used to show that the item is the same one seized and was not altered.

Introduction of foreign material, DNA, fingerprints, or other trace evidence into a scene or sample, which can weaken or invalidate forensic comparisons and interpretations.

Selecting appropriate containers and sealing methods for each item so that trace evidence is preserved, moisture is managed, and cross-transfer between items is prevented.

A scale drawing of the scene showing the positions of evidence, furniture, and reference points, typically prepared with measured distances or coordinates and labeled with a legend.

A measurement technique in which a straight reference line is established through or near the scene and each evidence item is located by perpendicular distances from that line.

A wide view image showing the scene or a major portion of it in context, usually taken before close-up work and used to establish where detailed images were captured.

An intermediate photograph framing an item of evidence together with enough surrounding context to show its position, bridging overall views and close-up detail shots.

A ruler or labeled scale placed beside evidence in a photograph so that dimensions and relative size can be determined later from the image itself.

Deriving accurate measurements or three-dimensional geometry from photographs using known camera positions, lens data, or reference scales included in the images.

Apparent change in size and shape of objects caused by camera angle and distance, which can mislead interpretation unless the camera is kept square to the subject.

The study of friction ridge skin using the biological properties of ridges, including their formation, persistence, and uniqueness, to support identification conclusions.

Individual ridge characteristics such as ridge endings, bifurcations, and dots; their number, type, and spatial arrangement are compared when linking a latent print to a known print.

A structured comparison method standing for Analysis, Comparison, Evaluation, and Verification, in which a later examiner independently reviews the conclusion reached by the first.

An impression of friction ridge skin left on a surface, usually invisible, that is developed with powders, chemicals, or light sources and then photographed or lifted.

A known fingerprint record collected from a specific person under controlled conditions, used as the comparison standard against which a latent or questioned print is evaluated.

A standardized record containing rolled and plain impressions of all ten fingers, used for identification, criminal history records, and comparison against latent prints.

Assigning a fingerprint to a category such as arch, loop, or whorl, with subgroups, based on the ridge flow and presence or absence of deltas and cores.

An automated fingerprint identification system that encodes ridge features from a print and searches a database for candidate matches, which are then reviewed by a human examiner.

A latent print development method in which fine powder is applied with a brush or atomizer so it adheres to oily residue, making the print visible for photography or lifting.

A chemical reagent that reacts with amino acids in eccrine sweat to produce a purple product, commonly used on porous surfaces such as paper and cardboard.

A two- or three-dimensional record of a shoe's outsole left in dust, blood, or soft ground, compared by pattern, wear, and accidental characteristics.

The manufactured design of ridges, grooves, and logos on a shoe outsole; it narrows the possible make and model before individual comparison begins.

Random, acquired features such as cuts, nicks, and wear on a shoe or tool that arise during use and support individual rather than class-level association.

A known print made from a suspect shoe or tool under conditions similar to the questioned impression, produced for side-by-side comparison and documentation.

Creation of visual products such as composite images, age progressions, and demonstrative exhibits to support identification, investigation, or courtroom explanation.

A facial image built from a witness's description using feature-by-feature selection or software, intended to help identify an unknown suspect.

An estimated update of a person's appearance over time, based on photographs and knowledge of aging, used in long-term missing-person and identification cases.

The number of image frames recorded per second in a video file; it governs playback timing and how time intervals between events are calculated.

A recorded timestamp or frame-count reference embedded in video that allows an examiner to cite and return to a specific moment during analysis.

Reviewing a video one frame at a time to track movement, count frames between events, and capture details that normal-speed playback would conceal.