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I am testing the quality of a fingerprint lifted with different materials used. 1.What conclusions can I expect? 2.What are good materials I can use to test and what are the procedures that follow?3.Is there new technology that helps investigators find the best quality of a fingerprint lifted?4. What do you do on a daily basis for your job?
Question Date: 2012-11-15
Answer 1:

A common way to lift fingerprints is to dust a powder over the suspect area of a material, let the powder stick to the oil, sweat left by the finger, and then lift the fingerprint with tape. When using this method, the important things to keep in mind are:

1. How well does the powder stick to the oils/sweat in the fingerprint?

2. How well does the powder stick to the surface which you are dusting for prints? Ideally, what you want is a powder that sticks strongly to the print, but does not stick at all to the surface. You can imagine that you wouldn't be able to lift a very good fingerprint if the powder also stuck to the surface in addition to the print! This means that you have to take advantage of the different properties of a fingerprint versus the surface which it is on. Fingerprints are made of mostly oil and sweat, so if your surface is something like glass, plastic, or maybe a metal door handle, you would want a powder that likes to stick to oil/sweat but not any of these other materials. You can experiment with several household powders like:

1. Pencil lead
2. Talcum powder
3. Corn starch

Pencil lead is a particularly interesting system. Pencil lead is made of graphite which is made up of carbon atoms. What you can do is get some mechanical pencil lead and crush it to a powder. Then, dust the powder over a surface (such as a glass) where you left a print. The pencil lead should stick to the fingerprint and not to the glass. Once you can see the print, you can take some clear tape and apply the sticky side to the fingerprint. When you pull the tape off, the fingerprint should now be stuck to the tape. You can then stick that tape on a piece of paper, and write a note of when and where it was collected (remember, you always have to label your evidence!). Now what you can do, is experiment with how much you crush the pencil lead and how well of a print you can lift (if you crush it to a really fine powder is it better than if the lead is still pretty granular? Why?). You can also do the same thing with the other powders. Another thing you can test is: does the age of the print affect your ability to lift a fingerprint with this method? In other words, if you press your finger to a glass, can you lift a print and hour later? Can you lift a print a day later? Can you lift a print a week later? If there is a difference, can you explain why?

In CSI like crime labs, forensic experts use many different techniques to lift prints. Some of them involve depositing a vapor on the surface which then reacts with chemicals in the fingerprint. Another method involves reacting ninhydrin with the amine groups in proteins in the fingerprint. When ninhydrin reacts with amine, it changes color (usually a purple color) which would then show where the fingerprint is. I work as a graduate student. This means that I split my time between going to class and doing research in a laboratory. In the lab, I use different chemical reactions to build new molecules and materials such as polymers. Polymers are very useful. Polymers are everywhere: plastic bottles, rubber bands, organic solar cells (polymers that convert light energy into electrical energy), and even DNA and proteins are all polymers. I enjoy my work, and I hope to design new polymers that can be useful and make the world a better place.

Good luck with your experiments!

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