Science can do many things - help us understand the world we live in, develop new technology, and even solve crimes! The science used to help solve crimes is called forensic science. Almost every scientific field could be involved in forensics in some way: chemists, psychologists, pathologists (diseases), botanists (plants), odontologists (teeth), entomologists (insects), and anthropologists (humans). So if you study forensics, you might use physics for comparing densities and investigating bullet impact; chemistry for identifying unknown substances, such as white powder that could be a drug; biology for identifying blood and DNA; and earth science for soil evidence.
Even with all the new technology we have to analyze a crime scene, one of the most important pieces of evidence is still a person's fingerprints! We leave behind fingerprints almost every time we touch something, and since every person has a unique set of prints, they are a great tool for identification. Look at your fingertips with a magnifying glass: The patterns you see are caused by ridges in the dermis, the bottom layer of your skin. These patterns are fully developed in human beings just seven months after conception, while still in the womb. The three typical patterns are loops (found in 65% of the population), whorls (found in 35% of the population), and arches (found in 5% of the population). While your fingerprints are different from anyone else's, fingerprint patterns tend to run in families. If your fingerprints are a whorled pattern, there's a good chance one of your parents has a whorled pattern too.
>> Download our Fingerprint Analysis Sheet to learn about the different types and features of fingerprints and to practice fingerprint identification!
Some fingerprints are visible - you can see marks left on a surface by dirty or oily fingers. Dusting is usually used for this type. Other prints are latent - you can't see them, but there are marks left by sweat, amino acids, and other organic residue from fingers. Fuming is often used for these. Do the following projects to learn both methods!
Hard surfaces often show fingerprints when dusted with a very fine powder.
Note: Fingerprint powder is very messy, so practice with it in a controlled area. Start out dusting a microscope slide to get the technique down and then you can move on to dusting other surfaces in your house.
Oils from your finger left an impression of your prints on the slide. When you brushed the powder off the smooth slide, some of it stuck to the oils, allowing you to see the patterns.
Another method for finding fingerprints is called "fuming." This works for many surfaces where fingerprint powder doesn't work so well, and also for prints on portable objects. With this technique, chemical fumes react with the organic substances in fingerprints (amino acids, etc.) to cause invisible prints to appear.
Note: Be careful with the superglue - get an adult's permission.
Certain chemical fumes react with the sweat and other organic residue left in latent fingerprints. The strong chemical fumes from the cyanoacrylate in the glue will react with the residue from your fingers. The chemical reaction causes the residue to turn white so you can see it. Professionals also use ninhydrin (which reacts with amino acids in latent prints) and silver nitrate powder developed under a UV light.