PROPERTIES OF BLOOD

• Jurisdiction: Australia

[97.150] Overview

This chapter is about the analysis of bloodstain patterns to reconstruct crime scenes and the advantages and limitations of that analysis. The physical properties of blood droplets which have produced a stain and their history before and after deposition on a stained surface are of fundamental importance in this analysis; however, it should be noted that informed crime scene bloodstain pattern analysis is not a trivial matter.

This is partly because blood is simply not a medium that easily lends itself to some aspects of analytical characterisation. It is often said to be a fluid like no other, and behaves differently depending on the condition of the victim or the location of the injury: Wonder (2007). Once external to the body, a number of complex mechanisms come into play which make the fluid unique. This fluid contains a cellular component which consists of red blood cells (erythrocytes), white blood cells (leucocytes) and platelets (thrombocytes) and a fluid component, plasma, which contains proteins, antibodies, nutrients and hormones.

White blood cells (leucocytes) contain DNA.

Red blood cells (erythrocytes) are red, biconcave discs manufactured in the bone marrow and are responsible for the transport of oxygen through the body. The colour is given to the cell by the "haem" sections of the haemoglobin molecule. Haem is forensically important as it is the catalyst for a number of the tests used for the detection of blood, but red blood cells do...