by David Lewman
As he looked around class, Corey couldn’t help but feel jealous when he noticed two or three kids using Quark Pads. Maybe I should ask for a raise in my allowance, he thought. Or get a job. One that pays a ton of money. . . .
Once everyone was seated and the bell had rung, Miss Hodges said, “All right. I’d like each of you to look at your left hand. What do you see?”
One kid said, “Jelly,” and got a laugh. Another said, “Dirt.” More laughter.
“Maybe I should have had you wash your hands first,” Miss Hodges said. “Look past anything messy that’s stuck to your hand. Pick just one finger and look very closely at the top section, above the joint. Now what do you see?”
All the students stared at their fingers.
“Little lines?” Kaylee said.
“Fingerprints!” Ricky Collins said. His mom was in charge of the cafeteria at Woodlands Junior High. She’d often complained about having to clean the kids’ greasy fingerprints off her clean counters.
“Fingerprints are what we’re going to study today,” Miss Hodges said. The class murmured, excited. “But fingerprints are what your fingers leave behind. Your fingers don’t have fingerprints on them, just like your feet don’t have footprints on them. Does anyone know what those little lines on your fingers are called?”
No one knew. Not even Ben, who often knew all the answers. It was strange to think that for years they’d known they had lines on their fingers, but they’d never even thought about what the lines were called.
“They are called friction ridges,” Miss Hodges explained as she wrote the phrase on the board. “They help our hands grasp things, the same way ridges and grooves on a tire help it grip the road. All humans have them, and everyone’s friction ridges are unique. Even identical twins have different friction ridges.”
Tossing the marker in the air and catching it, she asked, “Do any other animals have friction ridges on their fingers?”
Hannah raised her hand. “I think I read somewhere that koala bears have fingerprints that look a lot like human fingerprints.”
“That’s right, Hannah,” Miss Hodges said. “Very good! Koala fingerprints look so much like human fingerprints that it’s actually hard to tell them apart.”
“I love koalas,” Hannah added.
“Other great apes, like gorillas and orangutans, also leave fingerprints,” Miss Hodges continued. “And there are even some monkeys in South America that can leave prints with the pads on their tails. Their tails have pads with friction ridges, so they can use their tails to hang on to branches in the rainforest.”
She went on to talk about the history of using fingerprints to identify criminals. “Although people have known about fingerprints for a very long time, it was in the eighteen hundreds when they started to get the idea of using fingerprints to catch crooks,” Miss Hodges said.
She told the class about Sir William Herschel, an Englishman in India who kept records of his own prints for over fifty years and noticed that they didn’t change.
Miss Hodges talked about Henry Faulds, a doctor in Japan who wrote in 1880 about using fingerprints to identify criminals, and about Sir Francis Galton, who, in 1892, wrote the first book about fingerprints.
Ricky asked if all of this was going to be on a test. “Yes,” Miss Hodges said. Everyone started to take more notes.
After reviewing the history of fingerprinting, Miss Hodges told the class how fingerprints are analyzed by experts. She passed around magnifying glasses, asking the students to look for loops, arches, and whorls (kind of like tiny whirlpools) in their fingerprints. Experts use these features to put fingerprints in different categories. She told them the FBI has a huge database of fingerprints in a computer called IAFIS, for Integrated Automated Fingerprint Identification System.
Ben quickly found a whorl in the middle of his right index finger. Soon all the students were comparing arches, loops, and whorls. But the really interesting part was when Miss Hodges showed the class how to lift a print from a crime scene.
She had students run their fingers through their hair and then touch different surfaces—glass, marble, shiny painted wood. “Your fingers have pores that produce oil, so you can leave fingerprints without touching your hair, but doing it this way, we’ll be sure,” she explained.
“Especially you, dude,” one of Ricky’s friends said to him. For that he got a quick punch in the arm. Luckily for Ricky, Miss Hodges didn’t notice.
After they’d touched the surfaces, Miss Hodges had the students check them for fingerprints. Some they could see clearly. Others they could see more easily if they used a bright light.
“To help them see fingerprints,” Miss Hodges said, “investigators use special powders like these.” She brought out small jars of black, gray, and white powder. If the surface was light-colored, they used black or gray powder. If the surface was dark, they used white.
The students took turns using small makeup brushes to carefully apply powder to the fingerprints. “Don’t use too much powder,” she cautioned, “or you’ll cover up the print. And remember to brush very lightly, or you’ll smear the print.”
That’s exactly what happened the first time Corey tried powdering one of his fingerprints. But soon he got the hang of lightly dusting a small amount of powder onto the fingerprint, making it pop right into view! “Amazing!” he said.
“In an actual investigation,” Miss Hodges said, “you’d be taking close photographs of the fingerprints at each stage—before powdering, after powdering, before lifting, and after lifting.”
“Lifting?” Ricky asked. “How do we do that? There’s no way I can pick up this powder without messing it up.”
“Yes, you can!” Miss Hodges said, smiling. “You’re going to use a special tape.”
With a little practice, the students found that they could lift the fingerprint right off the surface with a piece of tape. “Again, you’ve got to be very careful not to smear the print,” Miss Hodges warned. “Keep your hands steady.”
After they lifted the prints, the students stuck them onto cards and labeled them. If they’d used white powder, they taped the print to a black card. If they’d used black or gray powder, they used a white card.
“Does everyone have a card with at least one of your fingerprints on it?” Miss Hodges asked. They all did. “And are the cards labeled with your name, the date, and which finger you used?” A few students scribbled quickly and then nodded.
“Good,” Miss Hodges said. “Now let’s try using the fingerprints for identification.” She split the class into groups of five. Each group had to choose one member to put a fingerprint on a glass slide. And it had to be a print from one of the same fingers the student had already recorded on a card.
As usual, Hannah, Ben, and Corey managed to be in a group together. Without saying it out loud, they chose Corey to put his thumbprint on a slide. They passed the slide around, so the other groups couldn’t see who had made the print. (Actually, the other groups were too busy doing the same thing to notice.)
Miss Hodges then had each group pass their slide and their fingerprint cards to another group. That group had to examine the slide under a microscope and decide which card matched the fingerprint.
“If you pay really close attention to the lines in the fingerprint, it shouldn’t be that hard to find the matches,” Miss Hodges said as the class worked. “But remember, investigators aren’t trying to match a fingerprint with just five other fingerprints. They’re looking for a match in a database of millions. That’s why they let computers do a lot of the work. But in the end it always comes down to a human expert to make the match.”
As they walked out of the lab after the bell rang, Ben said to Hannah and Corey, “That was a great class.”
“I know!” Hannah enthused. “It was like we were real crime-scene investigators.”
“And you know where would probably be a great place to look for fingerprints?” Corey asked. “On a metal box!”
&
nbsp; Corey spent the whole weekend thinking about fingerprints. On Sunday evening he texted Ben and Hannah to ask them to meet him at his homeroom the next morning. So on Monday morning Ben and Hannah went to their homerooms early and got permission to visit Corey’s homeroom. “Finally, we’re in the same homeroom!” Corey said happily.
“Well, for one day,” Ben said.
“It’s a start,” Corey said.
The three members of Club CSI had borrowed powders, brushes, tape, and cards from Miss Hodges. They explained to Mrs. Ramirez that they’d like to lift some fingerprints from the crime scene.
“Crime scene!” Mrs. Ramirez said. “I hadn’t really thought of it that way.”
“Has the thief returned the money?” Corey asked.
Mrs. Ramirez shook her head sadly. “I was hoping he or she would feel guilty and decide to do the right thing.”
“You haven’t called the police yet, have you?” Hannah asked.
“No,” Mrs. Ramirez said. “I’ve told Principal Inverno, but we don’t call the police for something relatively small like this, unless it’s absolutely necessary.”
“Well,” Ben said, “we’re not the police. But we’re hoping we can help solve this theft.”
Mrs. Ramirez thought a moment. “All right,” she said. “Let’s give it a try. I know everyone worked hard selling those magazine subscriptions, so it’d be a shame if they didn’t get to contribute all the money they raised.”
By now the other students had arrived in their homeroom. They were surprised to see Ben and Hannah up front, talking to their teacher.
“Class,” Mrs. Ramirez said. “Corey and the two other members of—” She turned to Ben. “What was the name of your club again?”
“Club CSI,” Ben answered.
Mrs. Ramirez turned back to the class. “. . . Club CSI are going to try to figure out who took the missing money. Let’s watch as they show us some of the techniques Miss Hodges has taught them in her forensic science class.”
As the whole class turned their attention to Club CSI, Ben, Hannah, and Corey felt a little uncomfortable. They hadn’t known Mrs. Ramirez was going to turn this into a demonstration!
“I hope we remember how to do this right,” Corey murmured.
“We will,” Hannah said reassuringly. “Don’t worry.”
They started with the desk. It was light beige, so they chose the black powder. As they gently brushed the handle of the desk drawer that held the metal box, fingerprints clearly popped into view. Mrs. Ramirez was impressed.
“Very professional,” she said. She invited the students to come up one by one to see the powdered fingerprints.
Throughout their investigation, Hannah took pictures with her phone.
After they’d found fingerprints with the powder, they lifted them with tape and attached them to white cards. They wrote “Desk Drawer” on the cards to show where the prints had been found.
“Now, of course, you’re going to find my fingerprints. I hope that’s not going to lead to my arrest,” said Mrs. Ramirez.
The students laughed.
Once Club CSI had gotten all the fingerprints they could off the drawer’s handle, they asked Mrs. Ramirez to open the drawer and then take out the locked box. They used different powders to find fingerprints on the padlock and the box itself.
The metal surface of the box was an excellent place to find fingerprints. So was the back of the padlock. Many of the prints were smeared (lots of people had handled the box), but several were really clear.
As they worked on powdering the prints, the team got better at it. They felt good, as though they really were professional investigators.
The kids in the class watched, fascinated. “Just like on TV,” one student murmured.
While the drawer was open, Hannah spotted something stuck in a crack between the drawer and the inside of the desk. She pulled it out.
“I think it’s a feather,” she said quietly. “Do you know where it came from?” she asked Mrs. Ramirez.
The homeroom teacher looked at the small feather. “No, I have no idea,” she said.
Ben and Corey needed help with the fingerprints, so Hannah slipped the feather into a plastic bag and then stuck it in her pocket. She didn’t want to make a big deal about the feather in front of the whole class. Everyone would probably have ideas about what it meant, and they didn’t have time for a long discussion.
After they’d gotten all the fingerprints they could from the outside of the metal box and the padlock, they asked Mrs. Ramirez to open the box. Then they carefully took out Jacob’s envelope, holding it by the edges.
“We really should have on gloves,” Hannah said.
“You’re right,” Ben agreed. “Should have thought of that.”
Paper wasn’t nearly as good as metal for holding fingerprints, but they gave it a try. Hannah brushed on the black powder. A few fingerprints were faint, but they showed up.
They lifted them with tape and put them on white cards, labeling them “Jacob Ritter’s Envelope.” Hannah included the date, too, wanting to be as professional as possible.
“Are those all the surfaces you wanted to cover?” Mrs. Ramirez asked. The club members looked at one another, then nodded.
“Now that you have all those fingerprints, what are you going to do with them?” she asked.
“Compare them,” Corey said.
“Against what?” Mrs. Ramirez asked, puzzled.
“Well,” Ben said, “we’d like to get fingerprints from everyone in your homeroom.”
“We’ve brought ink pads and note cards,” Hannah said, holding them out for Mrs. Ramirez to see.
“I see,” Mrs. Ramirez said slowly. “I don’t know.”
“It won’t take long,” Ben said. “Making fingerprints with an ink pad is much quicker than lifting a print from a surface.”
Corey turned to his classmates. “Is there anyone who doesn’t want to be fingerprinted? Of course, I’m going to be fingerprinted too.”
No one raised their hand. Corey, Ben, and Hannah had figured no one would refuse, even the thief. It would look suspicious. Of course, the thief might be nervous about being fingerprinted. They planned to watch everyone carefully to see if anyone was nervous.
But, actually, everyone seemed enthusiastic about the idea. They quickly lined up to be fingerprinted. As usual, Jean managed to be first.
As Club CSI had them roll their fingers across the ink pads and press them onto note cards, everyone seemed to be having fun. No one seemed nervous.
Ever competitive, Jacob tried to give the clearest, best fingerprint of all.
Even Mrs. Ramirez agreed to be fingerprinted.
Once they had everyone’s fingerprints on note cards and had carefully labeled them, the members of Club CSI politely thanked the students and teacher for their cooperation.
The bell rang. “Well, that was certainly an interesting start to the day,” Mrs. Ramirez said.
As the students walked out, Ben said, “What I’m really interested in are the comparisons. Do any of these cards hold the fingerprints of a thief?”
Corey, Hannah, and Ben met in the forensics lab. Miss Hodges had given them permission to use the lab’s magnifying glasses during a free period to compare the fingerprints they’d found at the crime scene with the fingerprints of Mrs. Ramirez and her students.
“So, what’s the plan here, exactly?” Corey asked.
“We’re going to see if any of the prints we lifted match the fingerprints on our cards, the ones with your classmates’ names on them,” Hannah said.
“Yeah, I get that,” Corey said. “But how are we going to do it? We can’t just start grabbing cards randomly.”
Ben nodded. “Corey’s right. We need some kind of system.”
After talking about it, the three friends decided to divide the prints they’d lifted from the crime scene into three equal groups—one for each of them. “Each of us will try to identify all the fingerprints in our
group,” Ben said.
“We could call these the Mystery Prints,” Corey said.
Next, they used the information Miss Hodges had taught them in class to put the labeled ink prints from the students and Mrs. Ramirez into groups. They spread the cards out on a table in the groups.
“And these are the Identified Prints. All we have to do is match up the Mystery Prints with the Identified Prints,” Corey said.
“Right,” Hannah agreed. “When you figure out who one of the Mystery Prints belongs to, write that person’s name on the card.”
Each of them took their stack of Mystery Prints and began looking at them carefully with a magnifying glass, comparing them, one by one, to the Identified Prints.
“Um, remind me,” Corey said. “What’s the difference between a whorl and a loop?”
“Target whorl or spiral whorl?” Ben asked.
“Either one,” Corey said. “Surprise me.”
“Well,” Hannah said as she peered through her magnifying glass, “a loop is a ridge that just doubles back on itself. Kind of like the loop in your shoelaces.”
“A whorl, on the other hand, is like a little whirlpool,” Ben explained.
Corey said, “Right. I remember that. But you’d be amazed how few whirlpools I’ve seen growing up in Nevada.”
“A target whorl looks like a target—a little circle with bigger circles around it,” Hannah said.
“Got it,” Corey said.
“And a spiral whorl looks kind of like a maze,” Ben said. “One spiral winding around another spiral.”
“Honestly? All these fingerprints kind of look like mazes,” Corey said, looking through his magnifying glass.
Hannah looked up from her cards. “I don’t know if this helps, but I start by looking at the center of the fingerprint to see if there’s a little circle or two spirals. If there isn’t, then I look for a loop. And if I don’t see a nice curved loop, I look for an arch.”
“Okay,” Corey said. “That does help. I’ll keep trying.”