1. April 17, 2014 Forensic Science Unit 3 Fingerprints
Take out your table of contents and turn to last page Fingerprints – principles, classes, and examples
Students will create a Modus Operandi
If time – Continue with your chapter 6 work
Objectives: Students will be able to classify their own fingerprints as loops, whorls, or arches

2. Unit 3: Physical-Personal Identification in Forensic Science
Fingerprints
Unit 3: Physical-Personal Identification in Forensic Science
T. Trimpe

3. Fingerprint Principles
According to criminal investigators, fingerprints follow 3 fundamental principles:
A fingerprint is an individual characteristic; no two people have been found with the exact same fingerprint pattern.
A fingerprint pattern will remain unchanged for the life of an individual; however, the print itself may change due to permanent scars and skin diseases.
Fingerprints have general characteristic ridge patterns that allow them to be systematically identified.

4. Each group is divided into smaller groups as seen in the lists below.
Fingerprint Classes
There are 3 specific classes for all fingerprints based upon their visual pattern: arches, loops, and whorls.
Each group is divided into smaller groups as seen in the lists below.
Arch
Plain arch
Tented arch
Loop
Radial Loop
Ulnar loop
Whorl
Plain whorl
Central pocket whorl
Double loop whorl
Accidentical

5. 60% of people have loops, 35% have whorls, and 5% have arches
Interesting Info
Fingerprint Factoid:
60% of people have loops, 35% have whorls, and 5% have arches
Did you know?
Dactyloscopy is the study of fingerprint identification. Police investigators are experts in collecting “dactylograms”, otherwise known as fingerprints.

6. Arches
Arches are the simplest type of fingerprints that are formed by ridges that enter on one side of the print and exit on the other. No deltas are present.
Tented Arches
Similar to the plain arch,
but has a spike in the center.
Spike or “tent”
Plain Arch
Ridges enter on one side and
exit on the other side.

7. Loops
Loops must have one delta and one or more ridges that enter and leave on the same side. These patterns are named for their positions related to the radius and ulna bones.
Radial Loop
Loop opens toward the thumb or the radial bone.
Ulnar Loop
Loop opens toward pinkie or the ulna bone.
Delta
NOTE: On the left hand, a loop that opens to the pinkie would be an ulnar loop, while one that opens to the thumb would be a radial loop.

8. Whorls
Whorls have at least one ridge that makes (or tends to make) a complete circuit. They also have at least two deltas. If a print has more than two deltas, it is most likely an accidental.
Central Pocket Whorl
Plain Whorl
Draw a line between the two deltas in the plain and central pocket whorls. If some of the curved ridges touch the line, it is a plain whorl. If none of the center core touches the line, it is a central pocket whorl.

9. Whorls – Part 2 Double Loop Whorl
Double loop whorls are made up of any two loops combined into one print.
Delta
Accidental Whorl
Accidental whorls contain two or more patterns (not including the plain arch), or does not clearly fall under any of the other categories.

10. Identify each fingerprint pattern.
Plain whorl ?
Double loop whorl A B
Radial loop
Right Hand
Left Hand
Tented arch
Plain arch C
Right Hand E D
Right Hand
Left Hand

11. It’s time to make some prints!
Avoid Partial Prints
GOOD PRINT Get as much of the top part of your finger as possible!

12. Directions
1st – Roll the “pad” portion of your thumb over the ink strip from the left side of your thumb to the right. You do not have to push down really hard!
2nd – Roll the “pad” portion of your thumb from the left side of your thumb to the right in the correct box on your paper to make a thumbprint.
3rd – Continue this process to make a fingerprint of all ten fingers on the “Modus Operandi” worksheet.
4th –Use your notes and a magnifying lens to help you figure out what type of pattern is found in each of your fingerprints. Label each one with the pattern’s name.

13. Problem:
Three weeks ago a local bakery was robbed at gunpoint. The thief wore a mask, so even when the police found a suspect the bakery owner couldn’t make a positive ID. However, as the CSI processing the scene, you collected several fingerprints from various parts of the bakery.
The police have identified a suspect, but he says he’s never been to that bakery. It’s your job to see if the suspect’s fingerprints match any of those recovered at the scene of the crime.

14. How do our fingerprint patterns compare to the expected averages?
Fingerprint Analysis
How do our fingerprint patterns compare to the expected averages?

15. How do our results compare to the averages?
Let’s determine the rate of occurrence for our fingerprint patterns ...
Pattern #
Total Prints %
Arch
Loop
Whorl
How do our results compare to the averages?
60% - Loops % - Whorls % - Arches
__% - Loops __% - Whorls __% - Arches
Write a paragraph on your worksheet that summarizes our results.

16. Let’s determine the rate of occurrence to compare males vs. females.
Pattern
# Male
# Female
Total
Prints %
Arch
Loop
Whorl
Which pattern is most common pattern among the males in this class?
Which is most common pattern among the females?
How do the averages for each sex compare to the expected averages?