Haemoglobin Species
Definition
The forms of haemoglobin relevant to bloodstain ageing: oxyhaemoglobin (HbO2, fresh), deoxyhaemoglobin (Hb), methaemoglobin (Met-Hb), haemichrome, and haematin; each has a distinct visible/near-IR reflectance spectrum.
- Fresh form
- Oxyhaemoglobin (HbO2)
- Oxidised form
- Methaemoglobin (Met-Hb)
- Later degradation products
- Haemichrome, haematin
- Detection method
- Visible and near-infrared reflectance spectroscopy
Common questions
Why does identifying the haemoglobin species matter for bloodstain age estimation?+
Each species forms in sequence as a bloodstain dries and oxidises, so its relative proportion in a stain acts as a rough clock, letting an examiner bracket how long ago the blood was deposited.
Can the haemoglobin species be determined without destroying the stain?+
Yes, reflectance spectroscopy reads the distinct absorption features of each species directly off the surface, so the method is non-destructive and can be repeated or followed by DNA sampling.
Does the sequence of species always run the same way?+
Broadly oxyhaemoglobin gives way to methaemoglobin then to haemichrome and haematin, but the rate depends heavily on temperature, humidity, and substrate, so the sequence is a trend rather than a fixed timetable.
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