In our experience, blood is considered to be by far the most commonly encountered body fluid in Forensic casework simply because the numerous acts of violence such as various types of assault, murder and sometimes sexual offences that occur, can each result in blood loss to significantly varying degrees.
In many of these cases, blood from the victim has the potential to be transferred to the assailant(s), although clearly that is dependent on factors / variables such as the use of weapons, number of blows inflicted, and at what stage during the assault bleeding commenced.
There are two general mechanisms of blood transfer namely:
- Direct physical contact with a bloodstained item or surface
- Blood being transferred in an airborne manner in the form of spots and splashes
Examples of the first mechanism include physical contact between an assailant and victim when that latter is bleeding, and standing in wet blood at the scene.
The transfer of blood by direct contact with a bloodstained item or surface can be primary, secondary or even tertiary transfer, and the presence of contact blood on a suspect’s clothing by no means solely implies that the suspect was directly involved in the crime, although other features of the bloodstain and the suspect’s of account events also have to be considered.
The second type of blood transfer requires some form of force to create the airborne blood and examples include simple gravity, repeated blows into wet blood, a blood stained weapon being swung about resulting in blood being ejected from the surface due to centrifugal forces, and blood from the nose/ airways of a victim being ejected.
The created airborne blood from the force that caused it can land on surfaces at the scene, and the clothing / footwear of individuals in close proximity including the assailants.
In many case, the nature, overall pattern, size, shape, volume and density of the airborne blood spots on clothing, footwear and other surfaces can very often provide important and valuable information as to its creation, the proximity of an individual to the assault, the relative orientation of the source of the blood, and the surface it has impacted.
Our blood pattern experts can examine clothing, footwear, weapons, and crime scenes (or photographs from scene) and provide expert opinion on the blood patterns evident.
Our findings can then be interpreted in light of the circumstances of a particular case, including relevant witness statements and a defendant’s account of events.