CSI: TFS

Identifying the culprits using blood testing.

At the suggestion of Mr. Elder, I put together a Crime Scene Investigation (CSI) simulation for one of our afternoon interim activities. Sixteen students were challenged to solve a murder/mystery using simulated blood tests, fingerprinting, hair analyses, and chemical tests for drugs. And the assailants and the victims were members of the group.

I set up the crime scene with four different lines of evidence — fingerprints, hair, blood, and drugs — and forensic methods, so I could break my students up into four groups. The students were all told that they were competing to solve the mystery; to find out what happened and who did what to whom. Without any coaxing, the groups each claimed proprietary rights one type of evidence and set about trying to solve the mystery on their own. Since none of the lines of evidence could explain everything from the crime scene they ended up having to combine what they all found.

A blood soaked murder weapon (also with fingerprints and hair sample).

The Crime Scene

There were two weapons lying on the floor: a bloody knife and a bloody rolling pin with a hair stuck to it. On the table above the weapons were a few lines of white powder. There seemed to have been originally four lines, but one and one half of them had been used. There were fingerprints and a strand of hair next to the powder lines.

Also on the table, close to the powder, were a deck of cards (with fingerprints), a set of poker chips, a scale, and another stray hair.

Fortunately for our detectives, the fingerprints and hair had already been pulled and tagged.

Acquiring the Evidence

It took quite a bit of effort to acquire and plant the evidence. Some of it, like the blood, was simulated, but I had to get the hair and fingerprints from the students themselves. Since the individuals who chose this activity were a self-selected fraction of the middle and high-schoolers, I wandered around the building at lunchtime at the breaks between classes trying to find one or two students who were by themselves or were in a group with others who had not chosen the CSI activity.

The crime scene setup really only requires evidence of two people, but to keep it a little more mysterious I used a little misdirection. I got five students to contribute fingerprints and hair, but told them all that they’d be the murderer. I also got one person who was not in the class to contribute as well so we’d have a set of completely mysterious evidence.

Fingerprints

I pulled fingerprints by having students rub their fingers on a black spot I’d created using a basic number 2 pencil. The student would get the black graphite on their fingers and then touch their fingertips to the sticky part of some clear tape. The fingerprints turned out quite clearly that way.

Since I did not have time to figure out how to transfer the fingerprints to the surfaces I wanted them on, I just stuck the pieces of clear tape where I wanted them in the crime scene, which also saved the detectives a bit of time and effort.

Once I told them how to get the fingerprints from their peers, the students did not need any other guidance about how to analyze the fingerprints. They took the imprinted sticky tape and stuck them to a sheet of white paper, where the black prints showed up quite nicely. Then they fingerprinted everyone in the classroom and compared, looking for whirls and swirls primarily, but also basing their conclusions on the size of the prints which they took to be indicative of gender.

Of the four sets of prints, they were able to accurately identify the two people who were holding the knife and the rolling pin. The misidentified the one set that was from a person not in the class, and could not find the match for the last set.

Interestingly, of the four students in the group, two did most of the work while the other two wondered off to join other groups.

Hair

Hair was easy enough to collect since the students were quite happy to donate one or two for the cause. One hair per student would have been sufficient, but I kept loosing them until I just decided I’d stick them onto a piece of clear sticky tape and leave the sticky tape with hair attached at the scene of the crime.

With only a little nudging, the group working on the hair realized that they could get out one of the compound microscopes to examine their specimens, and compare them to the students in the class.

One major indicator that helped with the hair identification was the length. Two of the hair samples were from girls with long hair, while one was from a fairly short haired boy. I did consider just leaving pieces of the hair as evidence, instead of whole strands, but it’s a good thing I did not since, for one reason or another, the hair group had a difficult time identifying the owners of their samples (lack of effort might have been one part of it). It did help a bit that the two major perpetrators of the crime were members of that group.

Drugs

My idea here was to simulate a drug (cocaine) deal gone bad because of a contaminated/cut product. I laid out three lines of corn starch to simulate the cocaine and one line powdered glucose in between the last two cocaine lines to represent the adulterated drug. I removed the last cocaine line and half of the glucose line to make it look like someone had been ingesting the lines and stopped part-way through.

The lines of powdered substance (cocaine) were severely disrupted by student's sampling, but you can still see the two full lines to the right and the half line that the spatula is touching. — The lines of powdered substance (cocaine) were severely disrupted by student’s sampling, but you can still see the two full lines to the right and the half line that the spatula is touching.

Since we’ve been testing for simple and complex carbohydrates in biology and chemistry classes I told the group testing the drugs that the test for cocaine was the same as the iodine test for starch: if you add a drop of potassium iodine to a starch solution then it turns black.

If the students had examined the drugs on the table closely enough they should have been able to see that the glucose line was different from the others; it was not as powdered (so the crystals were small but visible), and it did not clump as much as the corn starch. However, they did not, and I had to hint that they should perhaps test all the lines of powder instead of just the first sample they took.

When they discovered that one of the powder lines did not react with the potassium iodine, I told them that a common adulterant was sugar so they should perhaps test for that. One of the students remembered the Benedicts solution test, which they were able to easily conduct since I’d already had the hot water bath set up for them.

Looking through the United Nations Office on Drugs and Crime’s Recommended Methods for the Identification and Analysis of Cocaine in Seized Materials, it seems that a common test for cocaine (the Scott test) turns a solution blue when the drug is present, so the next time I try this I may have to find some tests that produce a similar color change.

Blood/DNA testing

Simulating the blood testing was one of the trickier parts of the procedure for my part since I had to keep things very organized when students started being sent to me to be blood tested.

The blood was actually a few drops of food coloring diluted into 10 ml of water. I used three drops of red in each case to try to at least get it to a somewhat blood-like color, but then in mixed in one or two other colors to get five unique blood types.

The number of drops of food coloring mixed with 10 ml of water to get the 5 blood types.

Type 1: 3 red + 1 blue
Type 2: 3 red + 1 green
Type 3: 3 red + 1 yellow
Type 4: 3 red + 1 green + 1 yellow
Type 5: 3 red + 1 blue + 1 yellow

To match everything up with the crime scene, I assigned Suspect A to have Blood Type 2, and Suspect B to have Blood Type 4. So a sample of Blood Type 4 went on the knife, and a sample of Type 2 went on the rolling pin.

As a result, when the blood type testing group wanted to blood test everyone in the classroom, I had them send the students to me one at a time and I handed each student a small cup with a random sample of one of the Blood Types, except for the two students whose blood were on in the crime scene. With 16 students, we ended up with three or four students with each blood type.

Blood type testing using chromatography. The little containers of food coloring can be seen to the upper left.

This blood sample -- from the rolling pin -- is beginning to separate into its constituent colors (red, yellow and blue). — This blood sample — from the rolling pin — is beginning to separate into its constituent colors (red, yellow and blue).

The students took their blood samples back to the testers who I’d shown a simple chromatography method. They’d cut out thin (< 1cm wide) strips of coffee filter, put a drop of the blood sample on the middle of the strip, and then taped it down to a sheet of clear overhead transparency film. Although any clear glass or plastic would have worked, the transparency film was nice because you could tape five coffee filter strips to one sheet and then loosely roll the sheet up and put one end into a partially filled beaker of water (see Figure above). Capillary action sucked the water up the strips and smeared out the blood samples so you could see its constituent colors. The method worked pretty well, and the students were able to compare the blood at the crime scene to their test results to identify the small group of people who shared the suspect blood types. It was a lot of work, and it would have taken much longer if the group doing it were not amazingly organized and worked extremely well together.

This method is more akin to blood type testing than DNA testing, which I’d have liked to simulate better, however I did not have the time to work on my chromatography method.

In Conclusion

It took a little coaxing to get them to the right conclusion in the end, but I and the student had a lot of fun solving the mystery.

The Math of Planting Garlic

Planting a bed of garlic at the Heifer Ranch CSA.

One of the jobs my class helped with at the Heifer Ranch was planting garlic in the Heifer CSA garden. The gardeners had laid rows and rows of this black plastic mulch to keep down the weeds, protect the soil, and help keep the ground warm over the winter.

Laying down the plastic using a tractor. The mechanism simultaneously lays down a drip line beneath the plastic for watering.

We then used an improvised puncher to put holes in the plastic through which we could plant cloves of garlic pointy side up. The puncher was a simple flat piece of plywood, about one foot by three feet in dimensions, with a set of bolts drilled through. The bolts extended a few inches below the board and would be pressed through the black plastic. Two handles on each side of the board made it easier for two people to maneuver and punch row after row of holes.

As I took my turn punching holes, we did the math to figure out just how much garlic we were planting. A quick count of the last imprint of the puncher showed about 15 holes per punch. Each row was about 200 feet long, which made for approximately 3,000 heads of garlic per row.

We managed to plant one and a half rows. That meant about 4,500 garlic cloves. With ten people planting, that meant each person planted about 450 cloves. Not bad for an afternoon’s work.

Arkansan Spiders

The Heifer Ranch is home to quite the variety of large spiders, including the tarantulas we found a couple years ago. Most of them work hard at keeping the insect pests down. Here’s a collection of some of them we ran into this year.

A green spider from near the Heifer global village's refugee camp. — A green lynx spider from near the Heifer global village’s refugee camp.

A brown spider found in the brush on the dam.

A wolf spider with babies on its back. Found in the grass near the foot of the dam.

Yellow garden spider found in the herb garden.

Heifer 2013

The partially completed version of the artwork that our students gave to the Heifer facilitators. The border pattern comes from the DNA Writer.

This year’s trip to the Heifer International Ranch was as excellent as it has been in the past. Students worked in their CSA garden (planting garlic and picking peppers and tomatoes for example), helped with maintenance on the grounds, assisted with taking care of their livestock, and spent a night at their global village. We saw quite the variety of spiders.

Each night, students spent a half-hour doing some reflective writing in their journals, and we had a discussion or lesson that tied into what they’d done or seen during the day.

Sunday: The geologic and geographic importance of rivers. I’d pointed out the all the agriculture on the Arkansas river floodplain when we’d crossed it on the drive down, so we talked about how rivers erode mountains and deposit rich soils on their floodplains, and how important those floodplain and deltaic deposits have been in the emergence of civilizations and the location of cities.
Monday: Language Arts. We took a short passage out of one of the students’ journaling to use as an apprentice sentence.
Tuesday: Global village. Our group ended up in the Guatemalan house and the slums. The dire situation in the sums evoked some moral flexibility.
Wednesday: Art: Drawing vegetables with watercolor and color pencils. We took advantage of having our art teacher along as one of the chaperones. Life in the slums: We also talked about the difference between our experience in the simulated global village and real life in the slums.
Thursday: Social interaction. We were paired with the Girls’ School of Austin, who invited us over for smores after our debriefing of the week’s activities by the facilitators. Our boys, in particular, learned how to start and maintain a conversation with people of the opposite gender.

Students also had a bit of time between lunch and the afternoon activities, which they spent playing games and looking at insects under the microscope.

On the last day, we talked about giving something to the heifer facilitators. One student suggested a coded bead string, but since we did not have any beads, we went with a drawing (see above) that was bordered by a DNA sequence giving the names (and symbols) of all the water-balloon babies the group had on their visit to the global village.

Situational Morality

“Stealing is always wrong,” versus, “If I were starving, I’d steal from A. no problem.” That was the gist of our discussion the evening after spending a night in the Heifer’s global village.

The “slum dwellers” had started off with very little in the way of resources, and two of them decided, on their own initiative, to steal some “milk” for their “baby” from the “Guatemalans” who were significantly better off. However, the rest of the slum group found out there was quite a bit of dissension in the ranks.

The thieves also stole most of the rest of the milk while they were at it to trade with the other groups. Their logic — I think — was that since all the groups needed milk, and they would be distributing it, then everyone could ultimately get what they needed, while if they had not stolen the milk then the slums might not have gotten any.

The reverberations throughout the all the houses in the global village were profound, however, lots of distrust and animosity developed that had not been there before. It made it more difficult for the slums to get the other resources that they needed, because the other groups could not trust their motivations.

In fact, the other groups ended up having a harder time trading and communicating with each other because of the breakdown in trust. One other group started to lie about what they had and did not have. At first this was to deter theft, but they quickly realized that they could use this to their advantage.

Interestingly, it all worked out in the end. The slum dwellers felt guilty enough to exhibit real concern when they thought their plan had gone wrong and one of the other groups did not have any milk. The Guatemalans ended up with enough resources of their own to have a decent dinner, and even passed on some of their left-over vegetables to the slums. The slums invited everyone over to the “christening” of their water-balloon baby and everyone came. And we got to have a richer discussion than if everyone had just been nice to everyone else.

You Can See the Stars From the Slums, Sometimes

I spent another night in the slums. With a different group the dynamics were a bit different. Since I was not to intervene, I spent some of my time taking pictures of the stars.

And pictures with light.

Grasshopper

I caught a grasshopper in the bushes this morning. They’re a bit of a pest at Heifer so I didn’t feel too badly about bringing it in to inspect under the microscope.

The students found it to be curious as well. So much so, that one decided — of her own volition — to diagram it as well; including one of the small fecal pellets our grasshopper had graciously deposited into its petri dish.

Exploratory diagram of a grasshopper (by E.H.).

When we get back, I’ll point out Cmassingale’s nice grasshopper dissection page. It’s a pretty decent reference for gross anatomy.

Students studying a grasshopper under the microscope. — Studying a grasshopper under the microscope.

Abby Stood

“On a particularly humid day, Abby stood, seemingly staring at the goat that was munching and crunching on oak leaves right in front of her. But really, she was contemplating the rather large fire-ant hill at her feet.” — by A.R.

So begins a rather curious short story, based on real-life events, in which a student faces a crucial, life-changing decision. Somewhat life changing for her, but rather more life changing for a bunch of ants.

This journal entry precipitated an impromptu language lesson that ended with a semi-official apprentice-sentence assignment.