Blood stain analysis

1. Blood stain analysis Objective: to understand how blood stains can give forensic scientists information about a crime.

2. blood • Blood is what moves oxygen around our body from the lungs to the organs that need oxygen and then back the lungs for more oxygen.

3. blood • Blood is made from three different parts in the plasma: • red blood cells, are transporters. The role of erythrocytes is to transport oxygen. To do this it produces great quantities of hemoglobin, which gives it the distinct red colour • white blood cells are defenders. The role of white blood cells is to defend the body against harmful bacteria and microorganisms. • Platelets are pieces of larger cells that have broken off in the bone marrow. They play a major role in haemostasis (control of bleeding) by plugging up a breach in a vessel

4. Bloodstain Analysis • By studying their position, shape and size, investigators can identify where the attacker stood during the assault, their height, how many times the weapon was used, and if the attacker was left/right-handed.

5. Finding the stains • To be able to use bloodstains at the scene of a crime to reconstruct an attack, investigators first have to find all of the stains. Investigators commonly use a high- intensity light beam, which when filtered, produces a violet light useful in locating bloodstains

6. luminol • Luminol after the suspect had cleaned the bath • Luminol and fluorescein are the most commonly used reagents and can reveal blood that has been watered down to a ratio of 12 000:1 i.e 12000 parts water to one part blood. Luminol reveals drops of blood when sprayed in a dark room. The luminol, on contact with bloodstains, turns fluorescent, making it visible to investigators.

7. Types of blood stain • Passive - formed due solely to the effect of gravity.  These include drips, pools, and clots (the last two being from venous bleeding).

8. Types of stain • Transfer - similar to the way a stamp transfers ink from an inkpad onto another surface, and the ink stain takes the shape of the stamp, blood from a hand or shoe will leave behind that impression.

9. Types of stain • Projected - due to a force, either within the body (internal, such as arterial spurts, as seen above), or from outside the body (external, such as cast off), which is greater than the force of gravity, thus allowing the blood to travel in a path other than merely one due to gravity.

10. Blood patterns • When a droplet of blood hits a surface, the shape of the mark when it lands reveals the direction in which the drop was travelling and the amount of force it was projected with.

11. Where did it come from? • Drawing direct lines to a point where they all meet is where the blood came from.