Mystery Science, Part V-B: How to Set up Fingerprints on Glass

In Advance

Fingerprints of the Suspects

You will need prints for each of the suspects and two prints on Mr. Body's glass. First, you need to get the prints for each of the suspects using the same method as in part A. To simplify this process, we are only going to work with one fingerprint from each of our suspects. (Otherwise you would have 70 prints to sort through!) You will need seven prints, one for each of our suspects and one for Mr. Body. You can get these seven prints by asking three people to give you the prints of their forefingers (index finger or finger closest to the thumb) and then one print from a fourth person. These could come from friends or other family member's prints. If you cannot get these prints, then you can use all your own prints from seven of your own fingers, but the prints will vary in size and look like thumb prints or pinkie prints, for example. You may have to eliminate some because they look too similar. Once you have made your prints chart, you will need to decide who you will assign to each print. Two prints will be found on the glass, and these you will label Mr Body's and Miss Scarlet's. The rest can be labeled randomly.

Fingerprints on the Glass

Now you need to get Mr. Body's and Miss Scarlet's prints on the glass. Since it is supposed to be the same glass that the contents we tested came from, you will need a similar glass as the one you used last week with the pH analysis. You need to use a glass, however, and not a plastic cup. First wipe the glass inside and out with a cloth to eliminate any fingerprints that might already be on it. Now rub the finger you will be using on the bridge of your nose or on your temples to pick up any natural skin oil. Press the finger onto the glass where you want the print to be.The print should be faintly visible to you at this point. If it is not, use a cloth to wipe the glass clean and try again. Put it in a plastic bag, without getting any additional prints on it or smudging the current prints. The bag needs to be large enough that the glass can fit in it and still be zipped shut.

With Your Students



Applying Fingerprint Analysis to Our Mystery

You need to "develop" the fingerprints, or make them so that you can see them so that you can compare and identify them. You will need to do this part for your students, letting them watch you as you explain what you are doing, as Super Glue or Cyanoacrylate is a dangerous gas if inhaled.

The glass is now in a plastic bag. Carefully pull the bag down touching the glass as little as possible. Get out your aluminum foil and your Super glue (or Krazy glue).

Squeeze about 5 – 8 drops of Super glue (or Krazy Glue) on a piece of aluminum foil and then quickly put it the corner of the bag.

To speed up the process, you can heat the bag with a blow dryer. Adding a moist (not wet) bit of paper toweling will also help.

Quickly close the bag and let it sit in a safe place.

Most prints develop within 20 minutes but some can take up to 24 hours.

Once you have developed the prints, have your students compare them to the prints of the suspects to make matches.

Try not to help them too much, even if they get it wrong, but answer any direct questions they might have. Don't forget to write the clues on your worksheet.
If your prints don't come out clear enough, you can go here instead.