Chapter 11: Fingerprints Flashcards
What are fingerprints?
- Ridges on toes, fingers, feet & palms
- Raised portions of the skin arranged in connected units called dermal/fricition ridges
- Purpose is to help us grip onto objects
4,000 years ago
1st known use as signatures on clay tablets
1700
Andreas Mayer 1st noted that no two fingerprints are the same
1856
Herschel noted that they didn change w age
1879
Bertillion began keeping fingerprints of police files
1888
Galton developed the fingerprint classification system in use today
1896
The Ten Card was invented allowing them to be used in criminal investigations from then on
Arches
- About 5% of all prints
- Have ridges that enter from one side & leave from the other w/ a rise in the center
- Plain arch > shows ridges entering one side/no angle/no pattern
Tented Arch
angle/can have a loop pattern/delta
Visible/Patent
left on smooth surface when blood, ink, or another liquid comes in contact w/ the hands and is the transferred to the surface
Plastic
indentations left in some soft material such as clay, putty or wax
Latent/Hidden
caused by the transfer of oils & other body secretions onto a surface. They are made visible b dusting w/ powders or making the fingerprints in some way more visible by using a chemical reaction
When do fingerprints form?
10 weeks into pregnancy
3 Classes of Fingerprints
loops whirls & arches
Loops
- 65% of prints
- Enter from the right or left & leave on the same side
- Has a core at the center and a delta (a triangular region)
Whorls
- 30% of all prints - look like a bulls eye w/ 2 deltas
- Plain Whorl - one or more ridges that make a complete spiral/2 deltas
Double Loop Whorl
2 separate loop formations w/ 2 deltas
Accidental Whorl
2 or more deltas & is the combination of 2 of the other patterns
1987
23 mil criminal fingerprint cards collected needed to be manually sorted
After 1999
matches in 2hrs
What is the AFIS?
FBI developed the Integrated Automated Fingerprint Identification System in 1999
What does the IAFIS do?
provides digital automated fingerprint searches, latent searches, electronic storage of fingerprint photo ales, exchange and test results
Methods to Visualize Latent Prints
- Ninhydrin
- Super Glue
- Silver Nitrate
- Iodine
- Fluorochromes
Ninhyrdrin
can be sprayed on paper. It reacts w/ amino acids in sweat to leave a purple print
Super Glue
(Cyanoacrylate)
can be heated in a vapor tent. It sticks to amino acids to get fingerprints in glass, metal, and skin
Silver Nitrate
wood or styrofoam objects can be dipped or sprayed w/ silver nitrate. It reacts w/ chloride in the salty sweat to show a print
Flurochromes
can be sprayed on non-pourous items and views w/ UV light
Iodine
can be heated in a vapor tent or a fuming gun to get prints off of paper, cardboard, and unpainted surfaces. It fades and must be photographed
What type of fingerprints need to be developed?
Latent
How do Children’s and Adults Prints Differ?
Children have shorter fatty acids and therefore evaporate quicker
Composition of Residue Left by a Latent Print
99% water, 1% fatty acids, salts, etc
What time span in which childrens fingerprints can be detected?
24hrs
