Area of Origin
Definition
The 3-D point in space where the blood-shedding event occurred, derived from the area of convergence plus the angle of impact for each contributing stain.
- Dimensionality
- 3-D point in space
- Inputs required
- Area of convergence plus angle of impact
- Discipline
- Bloodstain pattern analysis
Common questions
What can the area of origin tell an investigator about the incident?+
It estimates the height and horizontal position in space where the blood source was struck or the impact occurred, which can help corroborate or contradict a witness account of where a victim was standing or how a weapon was swung.
What sources of error affect an area-of-origin calculation?+
Stain selection bias, measurement error in individual stain angles, target surface irregularities, and the assumption that stains traveled in straight unimpeded trajectories can all introduce error, which is why analysts typically use multiple stains and report a zone rather than a single exact point.
Related terms
- Area of Convergence
- The 2-D point on a surface where the projected trajectories of multiple impact stains intersect. It's the floor-projection of the impact source.
- Cast-Off
- Blood thrown off a swung object (a hammer, a knife, a bat). The trail records the arc of the swing and often...
- Non-Newtonian Fluid
- A fluid whose viscosity changes with the shear rate. Blood thins under fast shear (a fast swing of a weapon) and thickens...
- Parent Stain
- The primary drop that produces a drip pattern. The smaller surrounding spatters are the satellite spatter; together they tell you about drop...
- Surface Tension
- The cohesive force at a liquid's surface that lets a drop hold a spherical shape in flight. Whole blood sits around 58...