What is forensic science? Forensic Science is the application of science to the law. It often involves police officers and scientists from many branches

What is forensic science?

• Forensic Science is the application of science to the law.

• It often involves police officers and scientists from many branches of science working as a team to solve a crime.

How did Forensic Science catch their killer?

How did Forensic Science catch How did Forensic Science catch their killer?their killer?

1. Why do you think it is important that ‘Most forensic scientists are not police officers’?

2. The evidence in this case was collected from 4 major sites – can you name them?

3. How long did it take the Forensic Science Service to process all the evidence?

Investigating Blood Spatter

Patterns

Categories of blood stainsCategories of blood stains

• Blood patters can be roughly grouped into 3 categories:

• Passive

• Transfer

• Projected

PassivePassive

These are drops created only by the force of gravity.

They can be further subdivided into

•Drops

•Drip patterns

•Pools

•Clots

TransferTransfer

• These occur when a wet, bloody surface contacts another surface. This may lead to a recognisable footprint or hand/fingerprint.

ProjectedProjected• This is where the source of bleeding is

subjected to another force – e.g. a blow or sudden movement. The size and shape of the drops produced depends on the size of the force.

What else can affect the patterns?What else can affect the patterns?

• The amount of blood

• The surface it lands on

• The height it drops from

• The direction it comes from

Blood on glass – no distortion

Blood on linoleum – distortion of edges

Blood on wood – lots of distortion

• Low velocity (1.5 m/s)– e.g. free-falling drops, cast off from

weapon

• Medium velocity (7.5 - 30 m/s)– e.g. baseball bat blows

• High velocity (>30 m/s)– e.g. gunshot, machinery

Types of Blood SpatterTypes of Blood Spatter

Investigating blood patternsInvestigating blood patterns

• Your task is to carry out an investigation to see if the height that blood drips from (passive) affects how big the droplets are.

Blood patterns resultsBlood patterns results

Height (M) Size of drop (mm)

Size of drop (mm)

Average size of drop (mm)

What is Forensic Science all about?

• Anthropology• Ballistics• Crime• Entomology• Evidence• Fibres• Trace

• Fingerprints• Odontology• Insects• Serology• Toxicology• Pathology• All about SCIENCEAll about SCIENCE!

Blood Spatter Analysis – extension higher ability

CSI

The origin is in the angle

History

• 1894 - Pitorowski wrote earliest reference to bloodstain pattern analysis

• 1939 - Balthazard was first to use physical interpretations of stains

• 1955 - Dr. Paul Kirk used bloodstain pattern interpretation as a defense witness in the Sam Shepherd case

• 1971 - Professor Herbert MacDonnell promoted bloodstain pattern interpretation as a tool for modern criminalistics

• 1983 – The International Association of Bloodstain Pattern Analysis was formed

Summary

What is Blood? Determining Distance of Blood Determining Direction of Blood Types of Blood Stain Patterns

What is Blood?

Introduction to Blood

Blood Spatter (or splatter)

Blood drops form different shapes and sizes

Blood spatter analysis uses the shapes and sizes to reconstruct the crime scene.

Determining Distance Blood Falls

Blood drops fall as small spheres

Blood Spatter > Distance


Drops form circle when hitting surface

Size depends on speed of blood drop



Faster drop = larger diameter (size)Higher distance = larger diameter

Due to air resistance, speed maxes out at distances above about 7 feet



However, size of drop also depends on the volume of the drop.

Volume depends on the object blood originated from (needle = small; bat = large).



Since the volume of blood is unknown…

The distance a drop has fallen cannot be measured.


Effect of Surface

Smooth surface = smooth sphere Rough surface may cause some

splatter

Blood Spatter

Determining Direction of Blood

Narrow end of a blood drop will point in the direction of travel.

Blood Spatter > Direction

Activity - 1

• Obtain the blood solution, dropper, protractor and paper plate

• Drop one drop of blood from 3 feet above the plate with the plate at 90 degrees to the dropper (i.e. 0 degrees on the protractor)

• Drop 3 more drops in different locations but with each subsequent drop decrease the angle between the dropper and the plate and either take a picture or draw what you see

• Record the angles used and observe the drops • Describe what you see

Angle (degrees)

Picture (Drawn or photographed) Picture observations

90 (0 on protractor)

Insert photo or drawing Describe in detail what you see

60 (30 on a protractor)






Conclusion

• Describe the relationship of angle of surface to blood pattern observed

• So angle angle of impact can be determined

Angle of Impact“The tail tells the tale”

• 90 degrees –

• 60 degrees –

• 30 degrees –

• 10 degrees –


If more than one drop (from spatter) results, the point of origin can be determined



If more than one drop (from spatter) results, the point of origin can be determined



This is a 2-dimensional point of origin. It is possible to determine the 3-D point of

origin



The angle can be determined mathematically.

Width/Length, then take the inverse sin (sin-1).

This number is the impact angle (90 = perpendicular to surface; <10 at a sharp angle)


For each blood drop, a string can be guided back to the point of origin.


Activity 2 3D blood splatter

• Determine the 3D angle of our blood spattered wall and the position of our victim

Types of Spatter

Spattered Blood = random distribution of bloodstains that vary in size Amount of blood and amount of force affect the size of blood spatter.

Can result from gunshot, stabbing, beating

Blood Spatter

Spattered Blood can:

Help determine the location of the origin of the blood source.

Help determine the mechanism which created the pattern.

Blood Spatter

Spattered Blood

In general, for higher impacts, the pattern is more spread out and the individual stains are smaller.

Low impact = beating High impact = gunshot

Blood Spatter

Types of Spatter

Gunshot Spatter = can result in a mist-like spatter that indicates a gunshot.

Not all gunshots will result in misting.

If misting is present, it is most likely a gunshot.

Blood Spatter

Gunshot Spatter

Gunshots result in back spatter (where bullet enters) and forward spatter (where bullet exits).

Blood Spatter

Types of Spatter

Beating and Stabbing Spatter = larger individual stains

First blow usually doesn’t result in spatter since there is not yet any exposed blood.

Blood Spatter

Types of Spatter

Satellite Spatter = free falling drops of blood that fall onto a spatter pattern.

These drips are usually much larger than impact spatter.

However, blood dripping into blood can create a spatter.

Blood Spatter

Types of Spatter

Castoff Pattern = Blood flung off of swinging object.

Can reconstruct where assailant and victim were positioned.

Blood Spatter

Types of Spatter

Expirated Bloodstain Pattern = Blood can accumulate in lungs, sinuses, and airway. Forcibly exhaled.

Can appear like beating or gunshot pattern.

May be mixed with saliva or nasal secretions.

Blood Spatter

Alteration of bloodstain over time

Blood dries and clots over time. Difficult to estimate the time the blood

exited the body. Clotted smears can indicate time of

movement.

Blood Spatter

• Blood analysis website

• Try to recreate some of these blood splatter patterns on A5 paper after reading through the website (without injuring any one please!!!!)

• You must consult your teacher when about to begin to ensure your safety

Activity 3

http://www.crimescene-forensics.com/Blood_Stains.html

Documents

What is forensic science? Forensic Science is the application of science to the law. It often involves police officers and scientists from many branches