FBI Unit Study + Experiment 1 {Forensic Science-Fingerprints}

Posted on December 29, 2012 at 2:10 PM

I can't wait until the first of the year to start sharing with you what we have been doing on our newest unit study.

I knew when the boys decided to study about the FBI that it was going to be a longer study because of how many sub-topics we had listed. It has taken us more like 6 weeks instead of the normal 4 weeks pace that I try to stick with. Taking fingerprints was a pretty easy experiment to tie in with this study.

Prior to fingerprinting, the Bertillon system of measuring offenders was used in identifying criminals. Mr. Senior 2013 likes anything pertaining to learning about civil or criminal law so this topic made for a nice day or two to spend reading about it.

It wasn't until July 1, 1924 that the FBI begin to manage fingerprint files for the nation under the leadership of J. Edgar Hoover.  Prior to that time it took as long as 20 to 30 minutes to measure an offender.  Interesting enough you could see where persons of the same race and similar build were being convicted of crimes they did not commit.

It makes me wonder what offender would sit or stand still long enough to be  measured, let alone get on a stool and kick one foot back.

Gradually, the FBI expanded their knowledge to include being able to detect latent fingerprints by laser. Latent fingerprints are prints left at the scene of a crime which can't be seen to the visible eye. The Bureau goes from using a very antiquated system like the Bertillon system to using state of the art lasers to detect marks. Once they utilized technology they didn't stop using it. So we started gathering what books and magazines we have at home to continue studying about law enforcement and technology too.

We pulled out some of these magazines that we love. How it Works is a British magazine that has so many facts, beautiful illustrations and tons of information in each one. Do you use any of these?  Pricey, but we love these magazines and they are keepers around our house as we collect them. The one about robots has facts in it about self destructing memory sticks and an explanation about how handcuffs work. Chain, keyhole, ratchet and pawl are all parts of a handcuff.


Then we couldn't wait any longer and had to go ahead and get started on something hands-on. I always grab my basic "go to books" that have been with me for years.

These books,  How the _____ Works are made by Readers Digest. I know, crazy, but they have been timeless while I have schooled and still have experiments we haven't done yet.

In How the Body Works is an experiment on making fingerprints that my oldest boys did when they were Tiny's age, so we knew right where it was. Tying in a spy or detective element makes it even better. So the objective to this experiment wasn't just to study the types of fingerprints but to see who "moved the glass".

Understanding the three main patterns called whorl {spirals}, arches and loops and the percentage of people in the world who have them makes for a great math assignment for your older kids.

......{Arch}...................... Loop...............................Whorl.................              

In the prints encountered approximately 25% - 35% are whorls,  5% -10% are arches and 65% - 70% are loops. If you had a co-op group or even in your own family, do the percentages. Obviously the more kids you have the longer it will take to figure out the percentage. It makes for a fun way to apply some math skills

After reviewing all of that, Tiny gathered all the supplies for our fingerprints.

  • sheet of colored paper
  • wide double-sided tape
  • talcum powder
  • magnifying lens
  • soft graphite pencil
  • spoon
  • felt-tip pen
  • glass
  • ruler
  • scissors
  • soft brush {uhmm clear throat here. Yes that is another one of my make up brushes that bit the dust.}
  • craft knife

While I do encourage all of you to have a high school senior set up and lead your experiment, I know

it is not always possible to have one on hand. I am telling you I have soaked up every minute we have had this year as I sit back and let him run things. Now that we are almost  to 2013, I have such mixed emotions about his pending graduation. I can't go sappy on you now though, he is not graduated yet.

After adding the double sided tape to your grid on the paper, mix the powder and some scraped graphite, Senior style.

Then get everybody's finger prints on the top grid after they take a dip in the graphite. (Walk away. Enjoy a cup of coffee, blog, go exercise, go read as your Senior has this one under control.)


After all the fingerprints are taken, label which prints belong to whom. Then have your youngest sleuth leave the room so you can determine who will be the offender and pick up/move the glass. Have your criminal move the glass so that his fingerprints only are on the glass. You usually have to wait some time until the oil returns back to your skin, or you can cheat like we did and add some oil to your fingertips.

Crazy kid. My sleuth leaves the room and comes back with his best sleuthing outfit. A must have to solve this crime. Tell me he is not soaking this up as he walks back into the room.

Of course the more sleuthing paraphernalia you have the better.

Use the mix of powder and graphite for the dusting powder.

Identify the prints and match to your premade grid.

Find your offending party.

With a little cheating "help" {oil on the offending party's fingertips} so that we could do the experiment all at one time, it made for a morning of learning about forensics fun. My older boys want to do this with iodine fuming too.

I'll be sharing our second hands on activity soon. Have you tried an easy or not so easy version of fingerprint matching before?

You know my obsession with quotes too. I love this one about fingerprints, such a terrific science lesson we had about them.

I love old books. They tell you stories about their use. You can see where the fingerprints touched the pages as they held the book open. You can see how long they lingered on each page by the finger stains.

~Jack Bowman~


Hugs and love ya,

Categories: Unit Studies, FBI Unit Study