Blood Stain Analysis

Blood Stain Analysis

Warning: Today we'll be looking at different ways that blood can end up at a crime scene and the patterns it creates. There will be pictures of blood and spatter.

Please let me know if you feel uncomfortable.

Blood Pattern Analysis

Blood pattern analysis is important because it can help to recreate crime event by determining how blood was deposited, the type of force used, and possible weapon types.

Poll

Take a guess...which blood stain do you think might have been caused by a brush of hair on a wall?

• A

• B

• C

• D

• E

Things that may affect what a stain looks like:

In groups, make a list of things you think may affect what a blood stain looks like

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There are various types of blood stains, for example:

• Passive: drops, pools, flows from gravity

• Transfer: from contact with a surface

• Projected: from force

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Types of Stain

Do a drawing of the pictures above and label the satellites, spines, and elongations.

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Drop Shape

Blood smears tend to start as drops, which become ragged at one edge, indicating the direction of travel.

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Drop Shape

​What do you notice about the shape of the blood stains?

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Drop Shape

Drop Shape

Stains created when blood is flung from a moving object are called cast-off stains.

The tail of an elongated blood drop points in the direction the blood was travelling.

Cast-Offs

Cast-offs can also show whether the assailant was left or right handed.

Assailant: a person who physically attacks another.

A blood spatter can go from left to right but that doesn't means the person used their left hand. They could've used their right hand and gone in both directions.

The zig-zag line shows the person was right-handed because it would've been difficult to cross the body starting from the left.

Cast-Offs

Effect of Different Surfaces

• Smooth, non-porous surfaces create round, well-defined bloodstains with clear edges

• Rough surfaces cause irregular stains with spines and satellite drops

• Porous surfaces absorb blood, leading to spread and blurred edges

• The rougher or more absorbent the surface, the harder the stain is to analyse

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• Reacts with iron in blood

• Can reveal cleaned up or old blood

• Also reacts with bleach, some metals, and plant materials

Luminol

• ​Iron in blood reacts to make oxygen which changes the pH and turns indicator pink

• Quick and easy but can give false positives with plant materials

​​Kastle-Meyer Test

Multiple Choice

Which type of bloodstain is created when blood drips due to gravity?

• Transfer

• Passive

• Projected

Dropdown

The Kastle-Meyer test turns bright ​

Select answer

when it detects blood.

Labelling

Label the parts of a blood spatter.

Drag labels to their correct position on the image

Elongation (Tail)

Spines

Satellites

Multiple Choice

Which of the following can be determined by blood spatter pattern analysis?

• Direction of origin

• Angle of origin

• Area of origin

• General velocity

• All of the above

Multiple Choice

The width of the blood drops helps an analyst determine the ______ of the origin of blood.

• Height

• Angle

• Speed

Multiple Choice

What blood spatter pattern is seen in the picture?

• Transfer/Contact
• Swipe
• Wipe
• Saturation

Hotspot

Identify the blood spatter drop that came directly from above (90°).

Hotspot

Identify the blood spatter that came from the highest height.