Bring Science Home A forensic science project
Key concepts Forensic science Chemistry Biology Introduction Background These invisible latent fingerprints are made of water, fatty acids, amino acids and triglycerides—in other words, they result from the oil and sweat that your skin produces naturally. To make them visible, you have to find a way to detect one of these substances present in the invisible fingerprint. The easiest method is called dusting, in which you use a very fine powder that can stick to the oil in the fingerprint. Once the fingerprint becomes visible, you can lift it from the surface with clear tape and transfer it to another surface to then take into the laboratory to analyze further. Other methods include using chemicals that react with the amino acids or water in the fingerprint; the chemical reaction results in a colored fingerprint, which you can then analyze easily. Many factors determine the quality of a fingerprint on a surface. One of the most important factors is the surface texture. Fingerprints are most easily detected on smooth, nontextured dry surfaces. The rougher or more porous the material the more difficult it will be to get good fingerprint evidence. Another factor is the skin condition of your fingertips. If they are very sweaty and oily, you are more likely to leave behind prints than if they are dry and clean. Test it yourself, and collect your own fingerprint evidence like a real crime scene investigator in this activity!
Your freshly washed hands have much less skin oil and sweat because they have been washed away with the soap and water. This results in a much less pronounced fingerprint. You might have had difficulties in collecting this fingerprint or may not have found one at all. On the other hand, if you apply hand lotion, which contains lots of oil and fat, this will make your fingertips much stickier, leading to a much more pronounced print. You should have seen a big fat fingerprint once you applied the powder to the surface where had you pressed your finger. If you compare all the prints you collected, the one with hand lotion should be most visible whereas the impression with your washed hands should be barely visible. If you did the extra activities, you might have noticed porous or rough surfaces or materials such as paper or textiles are not very good for collecting fingerprints. Considering your results, where would you look for fingerprints in your home? Did you find some? Cleanup More to explore This activity brought to you in partnership with Science Buddies Discover world-changing science. Explore our digital archive back to 1845, including articles by more than 150 Nobel Prize winners. Subscribe Now! |