Case File-Crime Scene Investigator 4-H Awesome After School Kits
Crime Scene InvestigatorCase File
Suspects:
Jack the Jock- Suspect was given this nickname because he loves to play sports, however, his grades are not that great. Your teacher told the coach that he made a D on his last test, and as a result, the coach as benched him for the big game Friday night. Police found a black magic marker in his desk. Jack’s marker is labeled “B” in the evidence bag.
Sammy Smarty-Pants- Suspect was given this nickname because he always makes an “A” on every math test. The police found a black magic marker in his backpack. Sammy’s marker is labeled “B” in the evidence bag. Sammy’s desk is behind Jack’s.
Penny Popular- Suspect was given this nickname because she is the most popular girl in the class. The teacher recently gave her detention because she was passing notes during a test. Detectives found a black magic marker in her purse. Penny’s marker is labeled “C” in the evidence bag.
Chromatography Background:
As a team, you will use a technique called chromatography to find out which marker wrote the note. Chromatography is a procedure that CSI’s use to separate a mixture into different colors. This is possible because different pigments in the mixture are different size molecules. These molecules travel at different speeds through water, or other solvents. By measuring how far these molecules spread, you can identify the marker that wrote the ransom note.
In the Crime Lab:
First, using a ruler cut the note into a strip that is 1 inch wide and three inches long. Put the rest of the note back into the evidence bag. Next, cut three more strips that are 1-inch wide and 3 inches long from a coffee filter. Punch a hole in the top of each strip, and label each strip 1, 2, or 3 to the right of the hole. One inch from the bottom, make a horizontal line with one of the markers. Use marker “1” for the strip labeled 1; marker “2” for the strip labeled 2, and marker “3” for the strip labeled 3.
Fill each cup with water up to the line marked on the cup. Place a straw through the hole in each strip, and balance the straw across the top of each cup, as show in the picture. Make sure that the ink on the strip does NOT touch the water! Wait 5 minutes, and then lay the strip on a paper towel to dry. Do this for all three strips.
While waiting for the strips to dry, conduct the fingerprinting activity.
Fingerprinting Background:
Almost every time you touch something, you leave a fingerprint. We have hundreds of pores on our hands, and our sweat, mixed with body oils and dirt, leave prints of our fingers behind. Since no two fingerprints are alike, crime scene investigators like to use fingerprints as a way to identify people. Fingerprints have been used this way for thousands of years. In ancient Babylonia, people would press their fingers into a clay tablet when conducting business instead of signing their name. In ancient China, fingerprints were used to seal important documents. Fingerprints were first used in the United States in 1903, and the first murder solved by using fingerprints by in 1911, when a burglar left his fingerprints behind in wet paint on a stair banister.
Prints that you can see with your eyes are called visible prints. Prints that are invisible are called latent prints. Plastic prints are fingerprint impressions that are left behind in something soft or sticky, such as soap, clay, or wet paint.
In the Crime Lab:
As a team, you will use the fingerprints to determine who committed the crime. To do this, you will need to compare the fingerprint patterns and classify them into one of three groups. There are three basic patters of fingerprints: the loop, arch, and whorl. With modern technology, police can use computers to compare fingerprints, but today you will use the “old fashioned” technique.
Arch PatternLoop PatternWhorl Pattern
First, practice identifying fingerprint patterns by making your own fingerprint. Label an index card with your name. On another card, use a pencil to make a large mark the size of a quarter. Be sure the mark is very dark, and then rub your right index finger over the mark to make your finger black. Press your finger on the sticky side of a piece of tape and tape it sticky side down onto the index card labeled with your name. Use a magnifying glass to figure out which fingerprint pattern you have.
Next, examine each of the suspects’ fingerprints. Decide which pattern each fingerprint has and record it on your crime report form. Examine the fingerprint found on the water bottle. Which pattern does it have? Record your findings on your crime report form.
By now, your coffee strips should be dry. You will need to compare the strips them by measuring the color spread. Record your data on the Data Sheet. Which strip matches the one that you cut from the note? Based on the color spread patterns AND the fingerprints, who do you think committed the crime? How do you know that? Record your decision on your crime report from and let your leader know that you think you have solved the crime, and decide who from your team will give the report!
CRIME REPORT FORM
Case #______
Report Prepared by: ______
What are you trying to find out?
Chromatography Evidence
Measure the color spread from each strip and fill in the table
Strip / Color Spread (measured in centimeters)Marker A
Marker B
Marker C
Evidence Note
Which marker produced the most similar color spread compared to the evidence note?
Based on the measurements, who do you think committed the crime?
How do you know?
Tape or staple the strips below:
Fingerprinting Evidence
How many people in your group had an arch fingerprint? ______
How many people in your group had a whorl fingerprint? ______
How many people on your team had a loop fingerprint? ______
Complete this chart:
Evidence / Type of FingerprintWater Bottle
Jack
Sammy
Penny
Based on the chromatography and fingerprint evidence, who do you think stole the teacher’s laptop?
How do you know?