The most fun forensic DNA lecture I ever gave…

Happened yesterday, to a group of fourth grade students for my friend R’s class. They spent the last couple of weeks talking about forensics. My talk was going to wrap up the unit.

Now, having been a forensic DNA expert for 5 years of my life, I have had to give testimony in court (about 25 times now) for cases I worked on. I really disliked courtroom testimony since it was the defense team’s job to discredit my work (fortunately, they never succeeded).

I’ve given tours of our laboratory to visitors and explained what I knew about each area (and what I didn’t know, I deferred to those who did).

I even guest-lectured for some biology students at a private university. That was really, really nerve-wracking because unlike anyone else I ever spoke to, they knew the science behind the technology and would recognize if I made a mistake.

But…all my past talks did not bring me quite as much satisfaction and utter joy that yesterday’s presentation did.

I spent the weekend preparing my transparencies (the school is in the middle of nowhere, and they are very low tech over there), some images I got from a former colleague at the crime lab I worked with, some awesome images I gleaned from the internet. I finally finished all the transparencies I wanted late Sunday night.

But it wasn’t until Monday morning at 6:30, that I decided the presentation needed something more. I decided it would be much more fun if I could bring props to help me explain some of the concepts. So, I started digging around the girls’ science kits and my cupboards and came up with some basic materials.

In the picture below, you can see some of my props.  I filled a large plastic test tube with water and red food coloring for a vial of blood, a squeeze bulb pipet, a cotton swab (for collecting cheek cells), a piece of filter paper with red ink spot on it, and our handy-dandy pasta and pipe-cleaner model of a piece of DNA.


I also went into my kids felt foods, and found a red “ketchup splotch” I made out of red felt.  Perfect for a blood stain.   I also grabbed a pair of kid scissors too.


On the drive over to the school, I started visualizing how I wanted the talk to go, and it came to me that I was going to say we leave traces of DNA whereever we go.   I decided I was going to fake a sneeze into a kleenex and hand it to the teacher (my friend R) and say, “could you hold this for me please?” and tell the kids, “that’s got my DNA all over it now”, and also I needed to chew a piece of gum for a while, and hand that over to the teacher as well and tell the kids, “that’s got my DNA all over it too”.  At some point, I was going to yank out a piece of my hair, and explain that DNA can be found at the root where it was stuck in the skin of my head.   I left early enough so I had time to stop at a gas station for a much needed pack of gum and some water.

I also came up with a “kid-friendly” crime that they could understand but not disturb them (they were, after all, only about 10 years old). I wasn’t about to talk about the violent crimes my work was used for. And it kind of evolved on the spot (which is kind of surprising because before yesterday, I wasn’t all that great at impromptu acting).   I was going to pretend that their teacher and I got into a fight, and that he gave the suspect (in this case, me) a nose bleed and I bled on his shirt and that I’d leave hairs on his shirt too for two types of evidence.  It was all coming together nicely.

It turned out to go exactly as I envisioned it.  And it wasn’t just me doing all the talking.  I had time for the kids to ask questions as I went through my transparencies.

As I started my talk, I had R sit close by because he was an integral part of it.   I started explaining what DNA was, where it came from, what it looked like (I had a transparency and the pasta model to pass around) how much of it was the same between people (giving us the characteristics that make us human) and how some of it was very different among people (making them look different from the friend sitting right next to them).  I asked them if they knew of any twins or triplets that looked exactly the same and explained to them that they looked exactly the same because of their DNA was exactly the same. I even passed around a picture of my three girls to show them how different they looked from each other (one red-head with blue eyes, one brunette with brown eyes , and one blond child with brown eyes) even though they came from the same parents (I’m brown haired and brown-eyed, my husband is blond and blue-eyed).

Here are the transparencies I used to explain where DNA came from and how it looks.

During this part of the talk, I said, “excuse me, I have to sneeze”, and I dramatically grabbed a tissue from a nearby box and sneezed, then balled it up and handed it to R.    R played along well and wrinkled his nose when I said, “that’s got my DNA all over it”.

I was chewing my gum while I said all this introductory stuff, and after the sneeze, I asked the class if they were allowed to chew gum in school.  Of course they said, “no”.   And I said, “hmm… I probably shouldn’t either”.    So I then turned to R and asked him if he was afraid of germs.  He said no, and then said, “good, can you hold this for me?” and plucked the gum out my mouth and placed it in his hand.  He gave me a very gross face and the kids all “ewwwwed” and laughed.   I said, “that’s got my DNA all over it too”.

I must say, I don’t think anything had EVER gone so smoothly and naturally and I was so relaxed and having fun with it, with the kids.  It was AMAZING.

Then we went on to the fake crime and I used the scenario that R was beat up, but that he punched the person in the nose and they bled on him and I stuck the bloodstain and a hair I yanked from my head on his light blue shirt (which was perfect because the red felt popped on that color).  Only I said he wasn’t sure he got a good look at me so he didn’t know that it was me.  I asked him if there was another girl teacher who looked a little like me (brown hair, brown eyes, similar build) and he said, “Ms.  L”.  Perfect.  So now we had 2 possible suspects and two pieces of evidence to analyze – blood and hair.

I went through the spiel of how I’d extract DNA from the stain, and had a transparency of the process.  I even went so far as to enlist the help of a student who held out her hands while I cut up a small portion of the stain, to get it ready for extraction, and how extraction was merely like cracking an egg open – opening up the cell wall to release the DNA inside.

Then I moved on to explain how they would get DNA from the suspects.  That’s where the tube of fake blood, the bloodspot on filter paper and the cotton swab came into play.  I told them that blood would be drawn into a tube, and then I’d take the squeeze bulb pipet and transfer a drop to the filter paper and extract if from the filter paper, just like the bloodstain.  But, then I told them I hated needles and I was a big chicken and that I didn’t want to give my blood, but that they could still get DNA from me, but collecting cheek swabs.    It was then that I used R to illustrate how I would do that.  I had him open his mouth, I swabbed his cheeks, then held up the swab and said, “now I can get DNA from his cheek cells”.

It was so cool.

Then I moved on to the hair analysis.  I really didn’t have any experience explaining how trace chemistry actually does what they do with hair and fiber analysis, but I ended up finding a great pdf file online of the process, so I printed out some of the slides they made.  In particular, the kids loved the one about how to determine microscopically if a hair was human or animal (because there are very different morphologies to the interior of the hair).  The kids were oohing, and ahhing about the way the cat, dog, mouse, rabbit,  rabbit and human hair looks so very different.  Then I had a color photo of a human hair and it was so neat.  I told them that after trace chemistry did their analysis, they’d turn over the hair to me and I’d analyze it for DNA.


I had a printout of an actual DNA electropherogram, and a data table to show the DNA results of the evidence and the DNA results of me and the other teacher who were suspects.  I had the kids help me determine the match.  And the really “got it”.

Here’s the slides I used to explain DNA extraction and the electropherogram and the data table.

I think I impressed the hell out of myself, that I actually put together a really quite amazing presentation in less than a weekend and that I was able to give a presentation so informative (yet at the level 4th graders could understand).

The talk, combined with letting the kids ask their questions all throughout the presentation, lasted exactly 1 hour, with additional time for them to ask more questions.  They had some really great questions and a few silly ones.  The most interesting question came from a boy who quietly told me that a friend of his had a third nipple, and that he saw it when they went swimming last summer.   R and I were both taken aback a bit by the question, and I can’t remember what answer I gave him, but something along the lines that DNA had something to do with that, but I wasn’t sure what.

Overall, it was a smashing success.  And it’s the kind of experience that makes me really want to teach science to kids for real.

Maybe it’s time I really think about getting that teaching certificate.  Perhaps I will think seriously about it if don’t get call back about the job interview I had 2 Mondays ago.

This entry was posted in career, combining science and motherhood, education, intellectual stuff, my secret dream, Uncategorized. Bookmark the permalink.

7 Responses to The most fun forensic DNA lecture I ever gave…

  1. Papa T says:


    Teaching certificate? As in “license?” Hmm… Ever thought about “non-State” schools where your education and expertise are “enough?”

    It looks to me like you taught this group quite well. And there’s no telling what these fourth graders picked up on. The presentation could very will have changed a life or two.


  2. raisingsmartgirls says:

    Thanks Papa T. I agree. I might have given them something they might remember for quite a while. Who knows where it will lead them. It felt good to be up there in front of the kids and making science come alive a little bit for them.

    As far as the teaching license goes. I am EXTREMELY hesitant to get a formal teaching license, for many reasons. I actually would prefer to teach at a non-state school (where I’d have more flexibility and autonomy), only I am not sure where they exist around here.

    There is a private k-8 academy near these parts (one that charges $10,000 a year for enrollement). Otherwise, I don’t know of any other types of schools unless I go to a Christian/Catholic type school.

    I don’t know if either one requires a teaching license.

    I do think there is lot of value in what I could teach kids. I know I would have a blast teaching them, and I know I want to get them very motivated about science. I’d want to teach middle school – mostly because I want the kids to participate in science fairs.

    I feel, I really would be a great science teacher, only I am uncertain how to make that happen other than the conventional route around here.

  3. raisingsmartgirls says:

    I wanted to add that our friend K came by with his fiance last night. When I talked to them how the talk went, after a bit he said to me, “You know, you should be a science teacher. You should see how your face is lit up right now just talking about science.”

    So yeah, maybe. Well see.

  4. Leah says:

    Excellent work!

    Regarding third nipples:
    Wikipedia summary: “A supernumerary nipple (also known as a third nipple, triple nipple, accessory nipple, polythelia or the related condition: polymastia) is an additional nipple occurring in mammals, including humans. Often mistaken for moles, supernumerary nipples are diagnosed at a rate of 1 in 18 humans.”
    discusses what (not very much) is known about heritability and associated conditions

    • raisingsmartgirls says:

      Thanks Leah!

      A triple nipple. Gosh that makes me ROFL.

      Thanks for looking it up.

      Oh, and that reminds me…
      Half the kids didn’t hear what the question was, and they said, “what did he say?”.

      I told them “I don’t think Mr. R would let me come back to the school if I repeated what he said” and laughed.

  5. J-viere says:

    This rocks!
    Well, Miss Casey, I am taking 21 credit hours next semester towards my biology major w/ teaching cert. Woooot! Four more semesters, baby!!

    Do it! Go for it! You’ll love it!

  6. raisingsmartgirls says:


    Thanks so much. It DOES rock! We’ll see how things go. I think I’m going to go to my old university and at least inquire about the requirements needed for a teaching certificate/license. Just to see how long it would take.

    If I don’t get the job, I will be taking some kind of classes. I need to do something other than sit at home dreaming and wanting to have a life outside the home.

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