  What are fingerprints? You have them, on your fingers and toes, and so does the rest of your family and everyone else in the world. Even some animals have fingerprints. If you examine the tips of your fingers with a magnifying glass, you will see that they are covered in little ridges of skin that make patterns. These patterns are formed on your fingers before you are born, and stay the way they are for your whole life. Nobody else in the world has a pattern like yours ... it's unique!The pattern is the same on all of your fingers, just sized differently. Even if you had an identical twin, his or her fingerprints would be different than yours! That means that we can identify people by the pattern of their prints, since everybody's are different. When you examine your own, you will notice that the ridges of skin seem to curve, and form complicated bends and twists. Your friend's fingerprints might curve in an entirely different way. Surprisingly, there are only about seven different types of fingerprints. Let's look at these now, and see if you can tell which type your own fingerprints are. Click on each one of the seven types listed below; when the window opens, compare your print to the type shown. Which type are yours?  You can print each of these windows too, to make comparison easier. In fact, it would really make it easy if you could make an image of your own prints; then you could compare pictures side by side.At the right you can see what a fingerprint picture looks like, and you can make one for your own fingerprints. You'll need an ink stamp pad and some clean white paper. Carefully roll one of your finger tips on the pad, making sure not to slide your finger as you roll it. (If you can get a friend to grab your finger and roll it on the pad for you, it will work better. Be careful not to get the ink on your clothes) Then roll your ink-covered finger tip on a piece of paper. If you do it properly, you should see an image of your pattern, like the one at the right. Then you can compare it to printouts of the seven types above and decide which type yours are! Remember that although there are only about seven different types of fingerprints, the many different ways that the ridges can come together or split apart make for a huge variety of different prints. No two person's patterns are exactly alike. Try to find a friend who has the same type of print as you do. Examine them closely and find the differences. Even two prints of the same type that look the same will actually be different if you look closely enough. This is what makes the science of fingerprint identification possible. Let's look at how fingerprints are left behind when you touch something. This is how criminals are caught! A person's fingerprints can be transferred to objects in three different ways:
 Try this: first wash your hands. Then run your fingers through your hair... just once.Now pick up a clean glass, and put it down. If you then examine the glass where you touched it, you will see that just touching your hair put enough oil on your fingers to leave a very good print on the glass. But how do police scientists get fingerprints from objects that aren't clear like glass? They apply a fine powder (usually aluminum) to the surface where they suspect a print might be. When they blow it off, the powder sticks to where the oil from your fingerprint ridges got deposited. They transfer this powder pattern using sticky tape to a piece of white paper, and there's the print for all to see! Nowadays they may take a digital photograph of the print so they can store it in a computer. However, they may also take a bit of the print itself, because any bits of skin left behind by the criminal can also help to identify them using DNA matching. You can try 'lifting' prints yourself. You'll need some powder; the graphite sold in little tubes as vehicle lock 'de-icer' works fine. Dark make-up powder will also work. You will also need a fine soft brush. A photographer's lens cleaning brush works great, because it will also let you squeeze a puff of air to blow away the excess dust. Get some sticky clear tape and some white paper too. Leave your fingerprint somewhere where you can see it, like on a clean glass or bottle. 
Blow a fine layer of powder over the print. Carefully brush the print so that it is completely covered by a layer of the powder. You must use a very soft brush and be gentle, because you do not want to smear the print. Next, blow away the excess powder.
Now press a piece of sticky tape over the print, being careful to press down gently, but not slide the tape, to avoid smearing. Peel the tape back, and apply it to the piece of paper the same way. You should have an easily visible recognizable pattern.
Let's have some fun using this technique. One person needs to be in charge. Get five people to make fingerprint samples on pieces of paper using the stamp pad method described above. Make sure everybody uses the same finger, and includes their name. Then the person in charge secretly tells one of the others to leave a print of the same finger on a clean glass.Now have someone lift the print from the glass; try to identify which one of you left it behind! You'll need a magnifying glass to check the prints carefully ... you will be looking for identical patterns and shapes. For example, look at the print at the left. Check for patterns like the loop (1) and the branching of ridges (2). Everyone's prints have these, but the exact position, size, number of branchings, and orientation, is different for everyone! Fingerprints have been used for many years to identify people. Sometimes the police will want to know who left prints behind at a crime scene. But there are other uses for fingerprints. Your prints identify you uniquely, so they can be used like a signature on documents. Some computer systems require you to put your finger in a slot so its print can be read electronically, before the machine will let you log on. Many laptop computers now do that too. Children's prints can be recorded in case of kidnapping. Certain occupations may require you to submit your fingerprints so that they can check to see if you have a criminal record. Fingerprint files of criminals have been kept on file by the police for many years. They used to have to check a set of prints by eye, looking through thousands of samples looking for a match. This was very time-consuming, and if the print was on file somewhere else, a match might never be made. Now, however, prints are stored as electronic pictures on computers, which police around the world can access. Computers themselves scan the millions of files very quickly, and can suggest possible matches. This means that fingerprints can now easily identify a suspect if their prints are already on file. |