IAI CP2 flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Impact spatter
- Blood dispersed by force; stain sizes vary with the energy of impact, typically 1–4 mm for medium-velocity events such as blunt force or stabbing.
- High-velocity spatter
- Fine spatter with droplets generally under 1 mm, associated with gunshot, machinery, or explosion; the small size reflects the high energy of the event.
- Low-velocity spatter
- Stains generally larger than 4 mm, produced by dripping or bleeding under gravity; larger drops and greater fall heights produce larger stains and more satellite spatter.
- Satellite spatter
- Small droplets that separate from a parent drop on impact; they travel further and land distal to the parent stain, following the parent drop's trajectory.
- Angle of impact
- The angle at which a blood drop strikes a surface; calculated as sin θ = width/length of the elliptical stain, with a circular stain indicating 90°.
- Directionality
- The pointed tail of an elliptical or exclamation-mark stain faces the direction of travel, while the rounded end faces the origin of the blood.
- Area of convergence
- The two-dimensional point where lines drawn through the long axes of stains intersect; it locates the source in the horizontal plane.
- Area of origin
- The three-dimensional location of the blood source, calculated as Z = tan θ × horizontal distance from the convergence point to the stain.
- Cast-off pattern
- Blood flung from a bloodied object in motion, producing linear trails of stains; the number and spacing of trails relate to the number of blows or swings.
- Arterial spurt
- A rhythmic, repeating pattern of droplets or spray following the cardiac cycle; often found on vertical surfaces and may show a spurting arc.
- Expirated blood
- Fine mist from the nose or mouth, often with air bubbles or mucus; distinguished from impact spatter by distribution and the presence of bubbles or saliva.
- Void pattern
- Absence of blood in an otherwise bloodstained area, indicating an object or person was present during the bloodshed and later removed.
- Drip pattern
- Free-falling drops produce circular stains on horizontal surfaces; on inclined surfaces they elongate, and greater fall heights produce larger stains.
- Transfer pattern
- Contact between a blood-bearing object and a surface; the resulting stain mirrors the shape and texture of the object, such as a shoe tread or fabric weave.
- Swipe pattern
- Transfer of blood from a moving bloodied object onto a clean surface, producing a directional smear that follows the object's motion.
- Wipe pattern
- A moving clean object passing through wet blood, often showing lighter streaks and feathering; it can alter or remove the original stain.
- Flow pattern
- Blood moving under gravity along a surface; direction is indicated by the leading edge and the trail left behind, and it reflects the surface's orientation.
- Pooling
- Blood collecting in a depression or on a horizontal surface; the pool's shape and edges can indicate whether the surface was level or tilted.
- Superimposition
- A stain that overlies another is generally later; overlapping stains establish the relative timing of deposition events.
- Stringing method
- Physically running strings from stains through the point of convergence to the calculated height; a demonstrative tool, not a substitute for trigonometric calculation.
- Presumptive test
- A screening test such as luminol or fluorescein that detects latent blood; a confirmatory test is needed to establish that the substance is blood.
- Confirmatory test
- A test such as Takayama or ABAcard that establishes the presence of blood; DNA analysis then identifies the donor of the sample.
- Luminol
- A chemiluminescent reagent that reveals cleaned or latent blood; it is destructive to some evidence and should be used after other collection methods.
- Chain of custody
- Documentation of each item, its location, and the collection method; bloodstained items should be air-dried before packaging to prevent degradation and contamination.
- Surface porosity
- Porous surfaces such as wood and fabric wick and distort stains, reducing edge sharpness; non-porous surfaces such as glass and metal preserve sharp edges.
- Photographic scale
- A scale placed in the same plane as the stain, used with a leveled camera and tripod to avoid perspective error in measurement.
- Raking light
- Oblique lighting that reveals faint stains and surface texture; diffuse light reduces glare on non-porous surfaces during photography.
- Measurement precision
- Record major and minor axes of a stain to the nearest millimeter and average multiple measurements to reduce error in angle calculations.
- Pattern classification
- Classify by mechanism (impact, cast-off, transfer, flow, drip, expiration, arterial, void) rather than by appearance alone; a single pattern may have multiple mechanisms.
- Terminal velocity
- Free-falling drops reach terminal velocity after roughly 2 m, so stains from greater heights do not grow proportionally with the fall distance.
- Typical blood drop
- A single drop typically holds about 0.05 mL and is about 4–5 mm in diameter when deposited on a non-porous horizontal surface from a low height.
- Drying and color
- Fresh blood is red; drying shifts color toward brown or black. Drying time depends on volume, surface, temperature, and humidity, so color alone cannot date a stain.