Oxygen deprived blood is not blue – it’s rich red

Learn Something New Every Day – Lecture 20 – Death Investigators

Oxygen deprived blood is a dark red colour. When it’s well oxygenated it is a brighter/vibrant red.

Veinous blood may look blue because of light diffusion through skin and livor mortis (lividity) makes the pooling of blood in a dead body look purple/blue for the same reason. So you’d expect someone suffering from carbon monoxide poisoning (where the blood fills with carbon monoxide and so has no room for oxygen) to have deep, dark red blood, right?

Not so. Their blood is cherry red (and victims of carbon monoxide poisonings take on a cherry red skin colour making them easy to diagnose).

This is because haemoglobin binds much better to C0 than 0 so as far as the blood is concerned it’s fully loaded (and therefore bright red) but oxygen can’t get a look-in and so the cells start to die.

‘Trails of Evidence: How Forensic Science Works” is a The Great Courses DVD lecture series