The physical properties of blood--forensic considerations.

An informed understanding and appreciation of blood related crime scenes is only achieved through practical experimentation of simulated blood spatter. Because of the increasing frequency of the HIV, Hepatitis B and C viruses, the use of human blood may be hazardous for those involved in such experimentation. Porcine (pig) blood has been cited by some as a reasonable alternative, and this paper presents a comparison of the physical parameters (surface tension, viscosity and density) of ageing pig and fresh human blood, under a variety of conditions, as well as measurements of droplet trajectories and stain patterns. The results support the use of porcine blood (up to two weeks old) in representing the behaviour of freshly spilt human blood.