3rd CSI lesson (21/7/11)

3 main fingerprint patterns

- Arch (0 delta)

- Loop (1 delta)

- Ulnar loop: ridges slope towards little finger

- Radial loop: Ridges slope towards thumb

- Whorl (2 deltas)

3 types of fingerprints can be found at a crime scene

Patent (e.g. Visible prints when fingers have blood on them)

Plastic (e.g. Indentations made in soft like material clay)

Latent

Methods of Lifting Fingerprints

- Super glue fumes

- Dusting powder (readily adhere to perspiration residues and/or deposits of body oils left on the surface)

- Silver nitrate spray (reacts with chloride in the salty sweat to show a print)

1st principle: Fingerprint is an individual characteristic

- No 2 individuals have yet been found to possess identical ridge characteristics

2nd principle: A fingerprint will remain unchanged

- It is unchanged during an individual's lifetime
- Even after injuries and burns the same patterns will return as the skin heals

3rd principle: Fingerprints have general ridge patterns

Observations:

• Compare the fingerprint patterns on your right and left hand. Are they mirror images of each other?

No.

• What kind of patterns do you see?

The thumb of my right hand is in a whorl pattern whereas the thumb on my left is in a radial loop pattern.

• Do the loops curve in the same or different directions in different fingers?

Different directions.

• Compare the size of the patterns eg. How many ridges make up a loop?