Lesson 2 Fingerprint
Pre-Lesson Reading
1.
Fingerprint Principles:
According to criminal investigators, the use of fingerprint follows 3 fundamental principles: a. A fingerprint is an individual characteristics because no two fingers have yet been found to possess identical ridge characteristics. b. A fingerprint remains unchanged during an individual’s lifetime. c. Fingerprints have general ridge patterns that permit them to be systematically classified.
2.
Origin of fingerprint: a.
Take a look at your fingertip. You’ll see small ridges made of skin. The ridges have a purpose. They help you get a better grip on stuff you pick up. b.
The ridges develop in the womb and remain the same throughout life, barring some sort of scarring or trauma to the deep skin layer. Although people grow and increase in size, the ridges became permanent and fixed in their patterns from about 17 weeks of embryonic development, ridge patterns do not change like other parts of our bodies. c.
When the finger touches a surface, perspiration and oils are transferred onto that surface, leaving a pattern called fingerprints.
3.
All fingerprints are classified into three categories on the basis of their general patterns: a. Arches

Ridges enter on one side and exit on the other side.

Approximately 6% of people exhibit this pattern b. Loops

Ridges enter on one side and exit on the SAME side.

Approximately 60% of people exhibit this pattern
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c. Whorls
 Consists of circles, spirals.
 Approximately 34% of people exhibit this pattern
4.
Types of fingerprint evidence: a.
Patent prints
These are clearly visible. They’re made when you touch something like paint or blood and then touch other surfaces. b.
Latent prints
They’re formed when you touch something and the oil and sweat on your hand leaves a print. Latent prints are mostly invisible to the naked eye.
Fingerprinting dust makes them visible. c.
Physical prints
These are made when you touch something like gum that leaves a clear impression of your prints.
5.
Three common methods of latent print enhancement: a. Lifting powder Application

Work bests upon smooth solid surface, e.g. walls, glass, knife.

Fingerprint powders are colored, fluorescent, or magnetic materials that are very finely ground and are brushed lightly over a suspected print to produce contrast to the background. These powders typically are available in black, white and other colors, including metallic.

Once the lifting powder has been successfully applied a fingerprint is then “lifted” using a wide piece of clear smooth tape. b. Iodine Fumigation
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 Work bests upon light-colored light weight/low density objects, e.g. paper, fabrics
 A small amount of iodine is placed at the bottom of a glass chamber.
The object bearing the suspected latent prints is then suspended from the top of the chamber. The chamber is then sealed and chemical reaction occurs. The latent fingerprints become dark brown in colour and photograph of the fingerprint will be taken.
WARNING: Iodine is irritating to skin and eyes. Do not breathe in iodine vapours. c. Cryanoacrylate Fumigation

Cryanoacrylate is a very strong glue. It has tendency to stick to the body oil residue found in fingerprints.

Work bests upon dark-colored dense objects, e.g. guns, knife handles.

When Cryanoacrylate begins to react with the body oil residue in a fingerprint, it leaves behind a whitish-grey film which is visible to the human eye. Photograph of the fingerprint will be taken.
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Lesson 2 Fingerprints
Worksheet 2.1 Fingerprint Basics
1.
Classify each of the following prints as loop, whorl or arch.
a. b. c.
2.
While searching a murder scene, you believe the following items may contain latent fingerprints. Indicate whether prints on each item should be developed using fingerprint powder or chemicals . a.
A leather sofa b.
A mirror c.
A painted wooden knife handle d.
Blood-soaked newspapers
3.
Fingerprints that deposited on a surface when oils and sweat are excreted from pores on the friction ridges are called ________________ fingerprints.
4.
The most common fingerprint pattern is the _________________ .
5.
True or False a.
The individuality of a fingerprint is determined by its pattern. b.
Fingerprints cannot be changed during a person’s lifetime. c.
Arches have type lines, deltas and cores. d.
Identical twins have the same fingerprints. e.
Computerized fingerprint search systems match prints by comparing the positions of bifurcations and ridge endings. f.
A fingerprint left by a person with soiled or stained fingertips is called a latent print.
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Lesson 2 Fingerprints
Worksheet 2.2 Practice the identification skills e.g. fork
Figure 1 ______________________________
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Instruction:
1.
Examine the fingerprint (Figure 1) with a magnifying glass if necessary.
2.
To which class does the fingerprint pattern belong? Write down your answer.
3.
Use Table 1 to help identify fingerprint ridgeline details. Locate and label at least 8 positions of ridgeline details in Figure 1.
Table 1 Fingerprint ridge details
Fork
Double Fork
Triple Fork
Delta
Dot
Bridge
Hook
Eye
Short Ridge
Ending Ridge
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Lesson 2 Fingerprints
Worksheet 2.3 Make a fingerprint
Apparatus and Materials:
(per group)
2 2B pencils
2 pieces of white paper
1 bottle of fine iron powder
1 adhesive tape
1 handkerchief
4 microscope slides
1 magnifying glass
Procedures:
Part 1 Patent fingerprinting
1.
Rub a 2B pencil over a piece of white paper until it is covered with graphite.
2.
Rub your index finger against your nose or forehead and place the finger at the center of the microscope slide.
3.
Press and roll your index finger firmly on the graphite pad and then press the finger on the tape thoroughly.
4.
Place the fingerprint on the worksheet.
5.
Repeat step 2 to 4 for another index finger.
Part 2 Latent Fingerprinting
6.
Use a handkerchief to wipe a microscope slide free of any stray fingerprints.
Handle the slide only by the edges.
7.
Rub your index finger against your nose or forehead and place the finger at the center of the microscope slide.
8.
Sprinkle the iron powder onto the edge of the print.
9.
Lightly shake the slide to apply a thin coating of iron powder onto the latent print.
10.
As the print becomes visible, you should shake the slide lightly until there is no excess iron powder on the slide.
11.
To lift the fingerprint from the slide, you should position the untouched portion of the tape above the imaged fingerprint and smooth the tape over the developed print.
12.
Place the fingerprint on the worksheet.
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13.
Repeat step 7 to 13 for the rest of your fingers.
Part 3 Statistics
14.
Identify the pattern of each your fingerprint.
15.
Write down the name of pattern under each fingerprint.
16.
Count the numbers of each pattern.
Part 4 Identify the ridgeline details
17.
Choose the fingerprint with best resolution among all your fingerprints.
18.
Examine the fingerprint with a magnifying glass.
19.
Use Table 1 of Worksheet 2.2 to help identify different fingerprint ridgeline details.
Results:
1.
Direct prints of your fingers
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2.
Latent prints of your thumb and index finger
3.
Among all your fingerprints, the numbers of each pattern are as follows:
No. of Arche s： __________
No. of Loop s： __________
No. of Whorl s： __________
Do all your fingerprints have the same pattern? ________________
4.
List out the names of ridgeline details you can identify. Count the frequency of each ridgeline detail.
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Group discussions
1.
Count the number of patterns of all fingerprints among your group. What is the population percentage of each pattern? Show your calculations.
2.
Which pattern is most common among your group members?
3.
Which color is the most popular color for fingerprint powder? Why?
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Lesson 2 Fingerprints
Worksheet 2.4 Try out the steps in analysing and comparing fingerprints
Case Profile
A suspect was arrested in a burglary case. When the suspect was fingerprinted, the desk sergeant noticed something very unusual
– his fingerprints somehow had been altered. The suspect admitted that he had peeled off the skin from one of his thumbs and transplanted it onto another thumb. The suspect even claimed that
“I have new thumbprints. I am a clean person.
”
Furthermore, the police have recovered an excellent latent thumbprint from an unsolved burglary case 3 years ago. There are some indications that these 2 cases may be related.
The recovered print and the suspect’s new thumbprints are provided for your analysis.
Can a match be made between the direct thumbprints from the suspect and the latent thumbprint found at the crime scene? Imagine you are fingerprint examiner and you need to evaluate the presented evidence, reach conclusions and provide findings in a report to the law enforcement authorities and the court.
Known left thumbprint from suspect
Recovered print from burglary scene
Known right thumbprint from suspect
The five steps in analysing and comparing fingerprints:
Step 1: Identify the general type of the central area of the fingerprint.
Step 2: Match fingerprint ridgeline details.
Step 3: Compare the unknown print and the known print, point by point, feature by feature, to see if they match.
Step 4: Evaluate whether the unknown print matches the known print or not.
Step 5: A second examiner verifies the results.
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Report
Known left thumbprint from suspect
Known right thumbprint from suspect
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Recovered print from burglary scene
Can the suspect be identified? Summarize your findings and report conclusions to law enforcement authorities and the court. (Paragraph 3 of Expert Testimony)
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Lesson 2 Fingerprints
Follow-up Activities
1.
Case study: Fingerprints on 2004 Madrid train bomb bag traced to Algerian
“Fingerprints found in a plastic bag containing detonators of the kind used in the March 11 Madrid train bombings were identified as belonging to an
Algerian national, police said Thursday evening..”.
Read the following or related articles and discuss what’s wrong with FBI’s case in one paragraph. http://onin.com/fp/FBI_LPOU_SLIDES_IAI_2008_AUG_18.pdf http://www.usdoj.gov/oig/special/s0601/PDF_list.htm http://www.usatoday.com/news/world/2004-05-20-algerian-madrid_x.htm http://www.foxnews.com/wires/2006Nov29/0,4670,SpainBombingsFBI,00.
html http://www.usatoday.com/news/world/2004-05-20-algerian-madrid_x.htm
2.
The following articles help you learn more about the history of fingerprinting.
Summarize them into a paragraph. a.
http://www.criminaljustice.state.ny.us/ojis/history/fp_sys.htm
b.
http://www.onin.com/fp/fphistory.html
3.
To learn more about the latest development in fingerprinting, visit the following website. List 3 new facts that you learn from this website. http://onin.com/fp/
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