finding bloodstains
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. If this method does not reveal blood or if the crime scene has been cleaned, other reagents that make blood identifiable are used. 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.
Luminol
The luminol, on contact with bloodstains, turns fluorescent, making it visible to investigators. Fluorescein is very sensitive and only glows if it is lit up with a UV light source. Both of these reagents react when they come in contact with iron that is found in haemoglobin in the blood.
origin of the stain
If blood is found on the wall, floor or ceiling it can often be traced back to where the attacker and victim were situated at the time. Originally, investigators analysed each mark and reconstructed its path using string. With present day technology being at a high standard, investigators now use computer programs that take gravity and the position of the blood into account and are able to chart an accurate flight path for the blood droplet.
blood splatter
Definite blood spatter marks often reveal even more information, particularly if the blood has been thrown from the tip of a weapon. Identifying whether the bloodstains curve to the left or the right reveals which hand the attacker used to hold the weapon and the width of the trail of blood can identify what type of weapon was used in the attack. Knives leave a narrow trail of blood whereas baseball bats leave a wider trail of blood.
The ability to effectively interpret bloodstain patterns is a science and an art. But, before investigators can dive into a crime scene, they must learn a bit of terminology, such as:
Angle of Impact – the angle formed between the direction of an individual drop of blood and the surface it strikes.
The ability to effectively interpret bloodstain patterns is a science and an art. But, before investigators can dive into a crime scene, they must learn a bit of terminology, such as:
Angle of Impact – the angle formed between the direction of an individual drop of blood and the surface it strikes.
projections
Blood that leaves the weapon can also indicate the viciousness behind the attack, as powerfully projected sprays of blood would suggest that the attack was frantic and unwavering, with the intention of killing in mind.
The absence of bloodstains is just as revealing as bloodstains being present. A space where no blood is present suggests that there may have been an object laying where the source of blood was projected and the surface to which the blood was projected onto. The object that may have been removed by the attacker will carry the same blood spatter marks as the rest of the area.
The absence of bloodstains is just as revealing as bloodstains being present. A space where no blood is present suggests that there may have been an object laying where the source of blood was projected and the surface to which the blood was projected onto. The object that may have been removed by the attacker will carry the same blood spatter marks as the rest of the area.