CSI EXAM 2: Blood Evidence and Bloodstain Pattern Analysis

Comprehensive vocabulary flashcards covering blood composition, fluid dynamics, bloodstain classification, mathematical calculations, chemical testing, and forensic documentation.

Bloodstain Pattern Analysis (BPA)

The process of identifying, documenting, defining, and analyzing bloodstains and patterns in order to provide an interpretation of the events that caused their deposition.

Cohesion

Forces that attract like molecules together, causing surface molecules of liquid blood to bond more strongly with each other than the air and producing surface tension.

Adhesion

The force that attracts unlike molecules together, such as liquid blood adhering to a knife blade.

Surface Tension

The tension between two fluids at a liquid–air interface caused by greater cohesive forces between liquid molecules than adhesive forces between the liquid molecules and air.

Contact Line Pinning

The phenomenon occurring as an impacting blood drop spreads into a disc-like shape, where viscous and surface tension forces are strongest at the contact boundary to resist spreading.

Drip Stain

A bloodstain resulting from a falling drop of blood that formed due to gravity.

Drip Pattern

A bloodstain pattern resulting from a liquid that dripped into another liquid, where at least one of the liquids was blood.

Satellite Stain

A smaller bloodstain that originated during the formation of a parent stain as a result of blood impacting a surface.

Accompanying Drop

A small drop of blood produced as a by-product of drop formation.

Drip Trail

A bloodstain pattern resulting from the movement of a source of drip stains between two points.

Pool

A bloodstain resulting from an accumulation of liquid blood on a surface.

Saturation

A bloodstain resulting from the accumulation of liquid blood in an absorbent material.

Flow Pattern

A bloodstain resulting from the movement of a volume of blood on a surface due to gravity or movement of the target.

Transfer Stain

A bloodstain resulting from contact between a blood-bearing surface and another surface.

Swipe Pattern

A bloodstain resulting from the transfer of blood from a blood-bearing surface onto another surface, displaying characteristics that indicate relative motion between the surfaces.

Spatter

Bloodstains resulting from an airborne blood drop created when external force is applied to liquid blood.

Impact Spatter

A bloodstain pattern resulting from an object striking liquid blood.

Forward Spatter

A bloodstain pattern resulting from blood drops produced when a projectile creates an exit wound.

Back Spatter

A bloodstain pattern resulting from blood drops produced when a projectile creates an entrance wound.

Misting

A bloodstain pattern resulting from blood reduced to a spray of microdrops as a consequence of the intensity of the force applied.

Expiration

A bloodstain pattern resulting from blood forced by airflow out of the nose, mouth, or an open wound.

Secondary Spatter

A stain caused by the deflection of blood after it makes initial contact with a target surface, resulting in a second stain.

Projected Pattern

A bloodstain pattern resulting from the ejection of blood under hydraulic pressure, typically from a breach in the circulatory system (such as gushing, spurting, or spraying).

Splash Pattern

A bloodstain pattern created from a large volume of liquid blood falling onto a surface.

Cast Off Pattern

A bloodstain pattern resulting from blood drops released from an object due to its motion.

Cessation Cast Off

A bloodstain pattern resulting from blood drops released from an object due to its abrupt deceleration.

Perimeter Stain

An altered stain consisting only of its outer edge characteristics after the central area has been partially or entirely removed.

Void

An absence of blood in an otherwise continuous bloodstain pattern.

Wipe

An altered bloodstain resulting from an object moving through a preexisting wet bloodstain.

Directionality

The characteristic of a bloodstain that defines the direction a droplet was moving at the exact moment it struck a surface.

Impact Angle Formula

The mathematical equation used to calculate the angle of impact ($i$): $\text{Impact Angle} = \arcsin\left(\frac{\text{Width}}{\text{Length}}\right)$, or the inverse sine of the minor axis divided by the major axis.

Area of Convergence

The space in two dimensions to which the directionalities of spatter stains can be retraced to determine the location of the spatter-producing event.

Area of Origin

The space in three dimensions to which the trajectories of spatter stains can be utilized to determine the location of the spatter-producing event.

Chemiluminescence

A process by which light is emitted as a product of heat caused by a chemical reaction, requiring no external light source (e.g., BlueStar).

Fluorescence

A process where energy is emitted and can only be visualized when illuminated by an alternate light source (e.g., Fluorescein).

Tetramethylbenzidine (TMB)

A presumptive test chemical that catalyzes a reaction with hemoglobin in blood to produce a blue-green color change.

Phenolphthalein

A presumptive test reagent where iron in hemoglobin catalyzes the breakdown of hydrogen peroxide to oxidize the reagent, creating a pink color change.

Leucomalachite Green (LMG)

A bloodstain presumptive test dye that interacts directly with the iron in blood hemoglobin to produce a green color.

Road Mapping

A photographic documentation method utilizing horizontal scales, vertical scales, and labeled metric rulers to preserve and map out bloodstain patterns at crime scenes.