Blood Pattern Analyses

In crimes of violence such as physical assaults and murder, loss of blood can be very common.

Blood is by far the most commonly encountered body fluid in Forensic casework, and not only can DNA profiles be obtained from bloodstains on footwear and clothing for example, but information can be obtained from these bloodstains that can assist in determining the mechanism of the deposition of any blood stains.

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 such as the number of blows inflicted, extent of blood loss, and at what stage during the assault bleeding commenced.

There are two general mechanisms of blood transfer namely:

  1. Direct physical contact with a bloodstained item or surface
  2. 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 (nose bleed for example) 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, including weapons, and the clothing / footwear of individuals in 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, and the relative orientation of the source of the blood and the surface it has impacted.

Many cases involving blood pattern analyses involves combinations of different types of blood transfer, and the ultimate interpretation of the findings has to be made in the context of the various allegations of the parties involved and the circumstances of the incident.

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.