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Forensic Science
Objectives◦ Discuss the history of
fingerprinting◦ Discuss the characteristics of
fingerprinting◦ Identify the basic types of
fingerprinting◦ Describe how criminals attempt
to alter their fingerprints◦ Determine the reliability of
fingerprints as a means of identification
◦ Explain how fingerprint evidence is collected
◦ Describe the latest identification technologies
◦ Determine if a fingerprint matches a fingerprint on record
◦ Use a process of lifting a latent print
Vocabulary◦ Arch◦ Core◦ Delta◦ Fingerprint◦ Latent fingerprint◦ Loop◦ Minutiae◦ Patent fingerprint◦ Plastic fingerprint◦ Ridge pattern◦ Ten card◦ whorl
Fingerprints as a means to identify individuals was a major breakthrough in forensic science
The objective of this activity is to produce a fully printed ten card, identify your fingerprints, and compare your fingerprints to those of your classmates
Loop
New tool to solve crimes, clear the innocent, and convict the guilty
Interesting fact – Identical twins have the same DNA, but has a unique fingerprint made up of whorls, loops, or arches.
Oldest known document showing fingerprints dates back to third century B.C.
Earliest known record of the study of patterns on human hands was 1684 by Dr. Nehemiah
In 1788, Johann Christoph Andreas Mayer explained how the ridges were never duplicated in two persons
In 1823, Jan Evangelist Purkyn described nine distinct fingerprint patterns
In 1879, Alphonse Bertillon used fingerprints to identify criminals and was used in 1883 to identify a repeating offender.
In 1902 he solved the first murder using fingerprints.
1888, Sir Francis Galton (who verified prints do not change with age) and Sir E.R. Henry developed a classification system for fingerprints that is still in use today
1891, Ivan Vucetich improved fingerprint collection. Noted measurements and took all ten fingerprint impressions
1896, Sir Edmund Richard Henry grouped fingerprints based on whether they had an arch, whorl, or loop pattern.
Each fingerprint card was imprinted with 10 fingerprints of a person and marked with individual characteristics, ten card.
All fingers, toes, feet, and palms are covered in small ridges, called dermal, or friction ridges
Can leave an impression called a fingerprint
The imprint of a fingerprint consists of natural secretions of sweat glands◦ Water◦ Oils◦ Salts◦ Everyday dirt
Skin is divided into three layers: Surface is called epidermis
◦ Thin layer (skin is shed)◦ Mostly waterproof◦ provides protection from bacteria
and viruses◦ Contains melanin that filters UV
rays from the sun The second layer is called the
dermis◦ Provides strength and flexibility◦ Contains nerve endings and,
sweat glands, oil glands, hair follicles, and blood vessels
The subcutaneous layer is the most internal layer of the skin◦ Provides insulation◦ Offers protective padding◦ Stores energy
Latest information suggests patterns are probably formed at the beginning of the 10th week of pregnancy
Occurs at the basal layer within the epidermis
Occurs because the basal layer grows faster than the epidermis and the dermis the layer collapses and folds in different patterns
Named for their visual appearance◦ Loops - 65%◦ Whorls - 30%◦ Arches - 5%
Two things a forensic investigator looks for:◦ Core – is the center of a
loop or a whorl◦ Delta – a triangular
region located near a loop
Investigators also look at ridge count.
The basic fingerprint patterns can be further divided.
Whorl patterns:◦ Plain whorl (24 %) ◦ Central pocket loop whorl (2 %)◦ Double loop whorl (4 %)◦ Accidental whorl (0.01 %)
Arch patterns:◦ Plain arch (4%)◦ Tented arch (1%)
Central Pocket Loop Whorl
Double Loop Whorl
Plain Whorl
Accidental Whorl
In order to positively match a print, more information is needed.
Every individual has a unique fingerprint resulting from unique ridge patterns called minutiae.
Recognizing those details in the differences between ridges, their relative number, and their location on a specific fingerprint is called fingerprint identification.
In order to match fingerprints, a minimum number of points of comparison are needed.
Patent fingerprints◦ Visible prints, are left on a smooth surface when blood,
ink, or some other liquid comes into contact with the hands and is transferred to the surface.
Plastic fingerprints◦ Actual indentations left in some soft material such as
clay, putty, or wax. Latent fingerprints
◦ Hidden prints, are caused by transfer of oils and other body secretions onto a surface. They are made visible by dusting with powders or making the fingerprints more visible using a chemical reaction
Criminals tried to devise ways to alter their fingerprints
Ex. 1930’s, John Dillinger tried to remove his fingerprints with acid->Fingerprints came back!
Many experts claim fingerprint identification is flawless
However, humans input and analyze data, and humans make mistakes
Results need to be checked and double checked to prevent false convictions
One study showed that 1 in 5 investigators make a false identification.
By 1987, the FBI had 23 million criminal fingerprint cards on file
Had to manually search, could take up to three months to find a match
In 1999, the FBI develop the Integrated Automated Fingerprint Identification System (IAFIS or AFIS)
Operates 24 hrs a day, 365 days a year, now takes up to two hours
47 million people are recorded in the data base
Dusting (drinking glasses, faucets, telephones, etc) with a fine carbon powder can make a fingerprint more visible.
Tape is used to lift and preserve it Also take photo of the print Metal or magnetic powders can also be used Chemicals can also be used to make latent prints
visible◦ Ninhydrin◦ Cyanoacrylate vapor (superglue)◦ Silver nitrate◦ Iodine fuming
Chemical Uses Application Safety Chemical Reaction Latent Print
Ninhydrin Paper Object Dipped or sprayed and wait 24 hours
Do not inhale or get on your skin
Reacts with amino acids (proteins) found in sweat
Purple-blue print
Cyanoacrylate Vapor
Household items: plastic, metal, glass, and skin
Heat sample in a vapor tent.
Do not inhale or get on your skin; affects mucus membranes
Reacts with amino acids
White print
Silver Nitrate Wood ,Styrofoam Object dipped or sprayed in silver nitrate
Wear gloves to avoid contact with the skin
Chloride from salt in perspiration on the print combines with silver nitrate form silver chloride
Black or red dish brown print under UV Light
Iodine Fuming Paper ,Cardboard & Unpainted surfaces
In a vapor tent, heat solid iodine crystals
Toxic to inhale or ingest
Iodine combines with carbohydrates in latent print
Brownish print (fades quickly)—Need to photograph
New scanning technology and digital system, fingerprints can be scanned at the rate of 500 to 1,000 dots per inch
Start investigating trace evidence picked up and left behind by our fingerprints (ex. explosives, cigarettes, drugs)
Biometrics is the study of using physical traits to identify people.