1. The Chemistry of Latent Print Development Techniques
Fingerprints
In the Legal Arena
The Chemistry of Latent Print Development Techniques

2. Portrait Parle’
A Verbal description of a perpetrator’s physical characteristics and dress provided by an eyewitness

3. Bertillon’s Anthropometry1883
Relied on Precise Skeletal Measurement
Rested on the Premise That Skeletal Measurements Were Fixed After Age 20
Utilized Photographs as Well as Physical Description

4. Bertillon’s Fall From Favor
Will West versus William West Case
Both men sent to Leavenworth
Only way to tell them apart was fingerprints!

5. Early use of Fingerprints
1. Chinese- Used fingerprints to sign legal documents
2.William Herschel- Required Indian citizens to sign contracts with imprints
3. Henry Fauld- 1880, suggested that skin ridge patterns could furnish infallible proof of identification

6. History Cont’
4. Francis Galton-1892 published 1st book on finger prints assigning 3 patterns ( loops, whorls, arches)
5. Sir Edward Richard Henry, developed modern system of classification still being used USA and Scotland
US adopted fingerprints use

7. Daubert Rules of Admissibility
1999 – fingerprint admissibility challenged in United Sates v Byron Mitchell
Defense attorney argued that under guidelines cited in Daubert, fingerprints could not be proven unique
Daubert hearing took 4 ½ days

8. Judge Determined
1). Human friction ridges are both unique and permanent
2). Human friction ridge skin arrangements are unique and permanent

9. The Primary Classification System
Part of the Henry System (basis of system used by FBI)
Using this classification system – all fingerprint cards in existence can be divided into 1,024 groups
Need to determine where the whorls are on “fingerprint pairs”. See text p. 396

10. Primary Classification System
Pair up the fingers like this: r thumb & r index, r middle & r ring, r little & l thumb, l index & l middle, l ring & l little
After establishing pairs, place the first one in the denominator, the second in the numerator to create a fraction
r index r ring l thumb l middle l little
r thumb r mid r little l index l ring

11. Look for the Whorl Patterns
Whorls in the first pair are given a value of 16
Whorls in the second pair, 8
Whorls in the third, 4
Whorls in the fourth, 2
Whorls in the fifth, 1
Now add the numbers together and add 1 to both the numerator and denominator

12. PRACTICE the Primary Classification System

13. Fundamental Principles of Fingerprints
1st Principle: A fingerprint is an individual characteristic; no two fingerprints have yet to possess identical ridge characteristics ( FBI has nearly 50 million records in the database)

14. How are fingerprints formed in the womb? | Ask Dr. Oz

15. Types of Fingerprints Left at the Scene
Latent – invisible until chemically treated
Plastic – left in soft material such as putty, wax, soap
Visible – fingers touch blood, dirt, grease or paint and then touch a surface

16. 2nd Principle Formed in the human fetus on the Dermal Papillae
A fingerprint remains unchanged during an individual’s lifetime
Formed in the human fetus on the Dermal Papillae

17. 3rd Principle
Fingerprints have general ridge patterns that permit them to be systematically classified

18. Iodine Fuming Iodine “sublimes”
Appropriate for porous surfaces, like paper
Must be photographed or “fixed” since prints will fade
Iodine “sublimes”
Resulting vapor combines with the Na+ ions in the print to form NaI

19. Ninhydrin Used on porous surfaces
Reacts with the amino acids in the fingerprint
Results in a blue-purple color

20. Superglue fuming
Used on non-porous items such as metals, electrical tape, leather and plastic bags
Superglue is about 98-99% cyanoacrylate ester a chemical that when heated will a create a fume that will adhere to a print

21. Fluorescence Expose fingerprints to laser light
Some components of perspiration will fluoresce
They absorb light and remit the light in longer wavelengths
Done in darkened room

22. Chemically Induced Fluorescence
Zinc Chloride after Ninhydrin
Rhodamine 6G dye after super glue fuming
Increases sensitivity to light exposure
Can now use high intensity alternate light source (ALS) instead of laser
Halogen or xenon-arc light passes through fiber optic cable and filters

23. DFO Replacement for ninhydrin 1,8-diazafluoren-9-one
Has been shown to develop 2.5 times more latent prints on paper than ninhydrin

24. Preserving Prints
Once latent print is visualized, must be photographed