SPATTERED BLOODSTAINS

• Jurisdiction: Australia

Introduction ................................................................................................... [97.1060]

Impact spatter ............................................................................................... [97.1070]

Firearm related backspatter .......................................................................... [97.1080]

Cast-off bloodstains ...................................................................................... [97.1090]

Vascular blood

Arterial ........................................................................................................... [97.1200]

Venous .......................................................................................................... [97.1220]

[97.1060] Introduction

Spattered bloodstains are a family of stains categorised by the ejection of blood due to an applied force, for example: those that may result from a physical assault or the breach of an artery. They are commonly found at scenes where significant bloodshed has occurred.

[97.1070] Impact spatter

The different dimensions of spatter bloodstains are a function of the mechanisms and levels of force used to generate their corresponding droplets. Their size range and the quantity generated from a single mechanism can vary considerably, depending on the original volume of the blood and the type and level of force applied. Impact spatter-type stain dimensions can typically range in size from less than 1 mm through to more than 5 mm. When found on a smooth non-absorbent or non-porous surface, they have either an elliptical or a circular shape. This depends on the angle of impact that the droplet makes with the target surface. A contact between a fast-moving blunt object and liquid blood on a flat surface leaves a distinctive pattern signature on that surface immediately adjacent to the contact area. For instance, a shoe striking a pool of blood or a bloodied hand slapping a wall will leave staining with characteristic spines radiating from the area of contact.

In earlier texts, which are still occasionally quoted, MacDonell (1982) proposed that spatter stains be characterised as one of three general "types": low, medium, and high velocity spatter. Velocity, rather than energy, was used to describe the nature of the mechanism that resulted in the blood pattern.

The "velocity" nomenclature approach has now been superseded. Analysts have redefined their position on the classification of blood spatter, opting for a classification regime based on specific features inherent in either individual stains or larger patterns rather than velocity ranges: see Figure 1.

All types of spatter have one aspect in common - their presence supports the proposition that the target surface was in reasonably close proximity to the blood spatter source. Very small droplets are substantially affected by air resistance severely limiting the distance they will travel (unless wind assisted): see [97.1600] and [97.1650]. Hence, smaller volume droplets are usually found closer to their source: see [97.1550].

It is important not to confuse impact spatter stains with satellite stains, which may also be referred to as secondary spatter. Satellite stains are those formed when smaller blood drops are thrown off from a parent drop when it strikes a receiving surface (or existing blood pool): see [97.1250]. Absorbent and/or textured surfaces such as...