Contact Traces: Blood

Contact Traces: Blood

• Serology: The study of blood and other liquids in forensics.

Taking a sample of blood off the car windscreen

What is Blood?• Makes up 9% of a person’s body weight.• The average adult has about 5 to 6 litres of

blood in their body.

Blood and Crime• Common evidence in violent crimes

What kind of violence would lead to blood traces?

http://www.staffs.ac.uk/schools/sciences/forensic/forensicfacilities/photography.jpg

Blood and Crime• Difficult to remove from a crime scene which

makes it very incriminating evidence

Blood and Crime• Tests for blood are so sensitive that they can show

up blood that isn’t visible to the eye.

A trail of latent blood made visible with the use of a reagent called luminol

Blood Groups• Discovered by Karl

Lansteiner in 1901.• Four blood groups

How is this useful in forensic science?

Blood Groups• Percentage of ABO blood group types in

Australia10%

38%49%

3%

B

A

O

AB

Blood Groups• Further categorized based on another antigen

discovered by Dr Landsteiner in 1927.

Blood Groups• Blood groups are inherited from your parents• Only the dominant group is expressed

A O

B

O

Blood Spatter: Prac this week• Examination of blood splashes and smears at a

crime scene tell a story (click below for video)

Blood splatter analysis

Dexter (click below for video)exterDe

Bloodstain patterns

1. Passive Bloodstains are caused by the force of gravity

Bloodstain patterns

2. Projected Bloodstains occur when some sort of energy or force has been transferred to the blood source.

Bloodstain patterns

3. Transfer/Contact bloodstains occur when a bloody object comes into contact with another object.

Blood splatter analysis

• http://www.youtube.com/watch?v=2UV_moaF45I

Determining Angle of Impact

DNA: Deoxyribonucleic Acid