Haemolysis
Definition
The rupture of red blood cells and release of haemoglobin into the surrounding fluid. In casework, haemolysis of aged stains, wet stains, or those in hypotonic environments releases haemoglobin and reduces the intact cellular source of nuclear DNA.
- Event
- Red blood cell membrane rupture
- Releases
- Free haemoglobin into surrounding fluid
- Common triggers
- Ageing, wetting, hypotonic environments
- Forensic consequence
- Loss of intact cells carrying nuclear DNA
Common questions
Why does haemolysis matter for DNA recovery from a bloodstain?+
Nuclear DNA for STR profiling comes mainly from white blood cells, and haemolysis itself lyses red cells, but the same wet or hypotonic conditions that cause it also degrade surrounding white cells, so a heavily haemolysed stain often yields lower quality template DNA.
Does haemolysis affect presumptive blood tests at a scene?+
Free haemoglobin released by haemolysis still reacts in tests like Kastle-Meyer or luminol, so presumptive testing usually remains positive even on a heavily haemolysed stain.
What scene conditions accelerate haemolysis?+
Prolonged wetting, submersion in fresh water, and warm humid storage all promote it, which is why wet-collected or poorly dried bloodstains are more likely to show haemolysis than stains air-dried promptly at the scene.
Related terms
- Haematocrit
- The proportion of blood volume occupied by red blood cells, approximately 45% in adult males and 40% in adult females. Influences the...
- Haemoglobin
- The iron-containing oxygen-transport protein in red blood cells, composed of four polypeptide subunits each with a haem prosthetic group. Its pseudoperoxidase activity...
- Methaemoglobin
- An oxidised form of haemoglobin in which ferrous iron (Fe2+) is converted to ferric iron (Fe3+), unable to carry oxygen. Its formation...
- Plasma
- The liquid fraction of blood (approximately 55% by volume), containing water, proteins (albumin, immunoglobulins, fibrinogen, clotting factors), electrolytes, glucose, hormones, and dissolved...
- Serum
- The fluid that remains after blood has clotted and the clot has been removed. It is plasma minus fibrinogen and other clotting...