Post on 02-Jul-2015
description
Fingerprints
Fingerprint origin
• During the third or fourth month of fetal development the sweat glands form in the skin through small pores. Pores link together to form a series of ridges that are unique to every individual.
How are fingerprints made?
• Materials are continually secreted from the pores in the skin within the ridges of the fingers.
• 98-99% of the secreted material is water and the other 1-2% is other organic and inorganic materials.
• Any sebaceous oils on the fingers is transferred from other areas of the body and is collected in the ridges.
• Other objects that have an oily or greasy residue also transfer materials to the fingers when touched.
• All of the materials that gather in the ridges can be transferred from the finger to the touched object…leaving behind a distinct fingerprint
Types of prints
• There are three types of prints that can be found at the scene of a crime.– Latent– Patent– Plastic
Latent prints
• Latent prints are considered to be any print that is not easily seen.
• They require Processing with the use of powder and/or chemicals like super glue fuming
Patent prints
• Patent prints are any print that can be easily seen because they were made with a substance on the fingers…such as blood, oil, or ink.
• Patent prints need to be photographed and then collected using lifting tape…they do not require chemicals
Plastic prints
• Plastic prints are three-dimensional impressions made in a substance that holds the shape of the ridges on the fingers such as putty, clay, or wax
• Plastic prints should be photographed first and foremost and then attempts can be made to get an impression using plaster or other casting materials
Analyzing prints
• In the past fingerprints were analyzed by fingerprint analyzers and then they would be compared to fingerprints on file.
• Now, computers do the work by digitally scanning prints into a large database called the Automated Fingerprint Identification System (AFIS).
• The computer uses an automated scanning device to convert the image of a fingerprint into digital ridge characteristics
What is analyzed?
• Ending ridge• Fork (bifurcation)• Island ridge• Dot• Bridge• Spur• Eye• Double bifurcation• Trifurcation
Ridge ending
Fork/Bifurcation
Island ridge
Dot
Delta & Bridge
Spur
Double bifurcation
Eye
Trifurcation