Questions and Answers
What is the primary objective of learning about fingerprints in crime scene investigation?
To identify the basic evidentiary value of fingerprints found at a crime scene
What affects the quality of fingerprint impressions?
The factors such as pressure, moisture, and oil
What are the three pattern groups used to classify fingerprints?
Arches, whorls, and loops
What is the purpose of obtaining both suspect and elimination fingerprint impressions?
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What is the standard method used to record fingerprints?
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What is the difference between rolled and plain fingerprint impressions?
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What is the purpose of locating, developing, and lifting latent fingerprints?
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What is the primary purpose of using the standard 10-print fingerprint card?
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What percentage of a fingerprint is made up of perspiration?
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What is the primary purpose of fingerprint classification systems?
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What is the purpose of using iodine fuming when obtaining fingerprints?
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What is the main advantage of using a flashlight to locate fingerprints at a crime scene?
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What is the purpose of using a glass plate when recording fingerprints?
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What is the primary reason for having a subject wash their hands before recording their fingerprints?
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What percentage of the population has arch-type fingerprints?
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What is the purpose of using powder and a brush to obtain fingerprints?
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What is the primary purpose of using a two-part system to record fingerprints?
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What is the primary advantage of using silver nitrate when obtaining fingerprints?
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What is the primary issue with using stamp pads for fingerprinting?
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Why should the subject's hands be washed before taking fingerprints?
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What should the finger printer do to ensure a good impression?
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What can cause mottled or patchy impressions?
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What should be done if a digit is missing?
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Why should the fingers be rolled from a strained to a comfortable position?
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What can cause ridge characteristics to be indistinct?
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What is the purpose of recording fingerprints in a specific sequence?
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Study Notes
Fingerprint Evidence
- A fingerprint is a deposit consisting of 98% perspiration, 1% amino acids, and 1% oil that forms on the friction ridges of fingers, palms, and feet and is left on a surface when contact is made.
Factors Affecting Fingerprint Impression Quality
- Condition of the hand:
- Must be clean and dry
- Age can affect the friction ridges
- Occupation of subject can affect the friction ridges
- Type of surface:
- Smooth, hard, clean surfaces are most likely to reveal prints
- Rough, porous, dusty, dirty, or greasy surfaces are least likely to reveal fingerprint impressions
- Atmospheric conditions
Fingerprint Classifications
- Fingerprints are classified into three pattern types and eight sub-groups:
- Arches (5% of population)
- Plain arch
- Tented arch
- Loops (60% of population)
- Radial loop
- Ulnar loop
- Whorls (35% of population)
- Plain whorl
- Double loop whorl
- Accidental "unusual" whorl
- Central pocket loop whorl
- Arches (5% of population)
Fingerprint Impressions
- There are three types of fingerprint impressions:
- Patent - visible
- Latent - invisible
- Plastic - molded
- Methods used to obtain fingerprints at a crime scene:
- Powder and brush
- Photograph
- Chemicals (iodine fuming, ninhydrin, silver nitrate, and super glue fuming)
Lifting Prints
- Precautions when dusting for fingerprints:
- Use good clean equipment
- Use the proper amount of powder
- Use a light movement of the brush
- After obtaining fingerprint impressions, they can be retrieved (lifted) with clear scotch tape and placed on a card and retained as evidence
Fingerprint Records - Rolling Suspect/Elimination Prints
- Standard 10-Print Record Card:
- Currently used by most law enforcement agencies
- Allows recording of basic pedigree information and rolling of all 10 digits
- Two-part system which records rolled prints and plain (PAT) prints
- Fingerprint Recording Equipment:
- Commercially manufactured kit
- Contains device for holding 10-print card, glass plate to hold ink, appropriate ink, ink roller, and cleaning material
Recording Process - Procedures for Rolled Impressions
- Have subject sign 10-print card and wash hands to remove perspiration and dirt
- Roll four fingers away from center of subject's body
- Roll thumbs toward center of subject's body
- Grasp digits with both hands and apply steady/even downward pressure
- Color of good impression should be dark gray, not black
- Impression should be roughly square in shape and fill appropriate digit box
Recording Process - Procedures for Plain (PAT) Impressions
- Have subject sign 10-print card and wash hands
- Have subject stand to immediate rear of officer
- Subject should hold fingers together straight and stiff
- Hand and wrist form level plane/no break at wrist
- Finger printer hold wrist and presses fingers simultaneously on ink pad, then onto print card in appropriate box
