First, let's discuss the skin and what makes a fingerprint possible. You have 5 layers of skin on the outside of your body called your epidermis. Now, go and tell everybody: HEY! YOUR EPIDERMIS IS SHOWING! Beneath the epidermis is the dermis. Check out the layers of your skin in the diagram below...
See where the red arrow is pointing to? That is part of the dermal layer, otherwise known as the papillary layer, pushing up into the epidermis. See how that looks wavy? Well, those 'waves' are causing the epidermis to form ridges. These epidermal ridges form the fingerprints on the surface of your skin and each person, besides genetically identical twins, will have unique patterns of these ridges.
You might ask: why do you have these epidermal ridges here and say...not on your face? Well, you need extra sensory receptors (the structures that receive sensations from the environment) in your fingertips so you can detect the slightest stimuli in your environment. See the 'tactile corpuscle' in the dermal papilla up there in the diagram? Well, these, along with some other sensory structures, are in great numbers in the dermal papilla. They're right next to the epidermal layer because they want to get close to the action on the outside. They want to pick up the sensation of you feeling something really soft...or maybe even a hot stove! Ouch!
Also, how would you be able to pick up anything or turn a page of a book if you didn't have some type of ridged surface on your fingertips. You'd drop things way more than you ever thought about if you had smooth fingers. These ridges also serve a purpose to allow you to have fine grasping and holding skills. Whew! I'm thankful for that!
Alright, we've established you have epidermal ridges and they are formed so you can feel things better with your fingertips. Great...so what in the heck does that have to do with fingerprints left at a crime scene?
Look back to the diagram above and you'll see what is called a sebaceous gland. These glands are oil glands and are associated with each strand of hair on your body. You might not have hair on your fingertips but you have hair nearly everywhere else - you are pretty oily! Your fingers pick up these natural oils and leave a residue each time you touch something such as a table, doorknob, a candy wrapper, a piece of paper...essentially anything can pick up fingerprints!
LET'S GET INTO SOME FORENSIC SCIENCE NOW!
- Minutiae defined: take a minute and look at your finger tips. Do you see the tiny lines that curve, arch, whorl and make loops? These are called friction ridges or epidermal ridges as we discussed above. When you see a 'canal' or a narrow valley, that is called a groove. When you see a hill or a raised portion, that is the epidermal ridges. The pattern of grooves and ridges are what we are going to focus on now.
- Let's discuss the general concepts now: you are born with a set of prints and these prints remain with you throughout life. As a child, your fingerprint might not 'last' on a surface as long as when you are an adult - but it's still the same print, nonetheless.
- The first thing that an investigator will do is to group the overall ridge pattern of the print into an Arch, Whorl or Loop. From there, there are plain and tented arches, spiral and target whorls, double loops and single loops. (See below for the examples).
- Second, smaller details are viewed such as ridge endings, short ridges, bifurcations. Once an investigator makes the appropriate number of matches with a known to an unknown, the criminal is in big trouble!
- There is a database now that enables investigators to make nearly an instant match after uploading a print into the computer software. The database is called AFIS (Automated Fingerprint Identification System). Now what might have taken a detective years to find...she can find in minutes if not seconds!
Groundbreaking technique in fingerprint technology
http://video.news.sky.com/skynews/video/ It could be a plot from a Hollywood blockbuster. But a real life groundbreaking technique called "fingerprint visualising" could help solve a murder case on America's Most Wanted list. And it's all thanks to a British forensic scientist. Sky's Darren Little explains.
How to take a suspect's fingerprints
Further info: http://bit.ly/oy4Ytd LJMU Forensic Science Lecturer Phil Gilhooley demonstrates how to take a crime suspect's fingerprints using the traditional ink and paper method.
How to dust for fingerprints
Further info: http://bit.ly/oy4Ytd LJMU Forensic Science Lecturer Phil Gilhooley demonstrates how to find and extract fingerprints from the scene of a crime.
How to Compare Fingerprints - The Basics
How to Compare Fingerprints - The Basics In this first lesson of fingerprint comparison we: - Define terms: ridge, core, delta, arch, loop, whorl, ridge ending, bifurcation, dot - Use the ACE process of fingerprint comparison: analysis, comparison, evaluation