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The Biology of Hair and Forensic Science
I hate to admit that I have been following the Casey Anthony case on TV. There is method in my madness though. The discussion of the forensics of hair is a great way to teach some interesting inquiry, biology and chemistry.
Fifteen years ago I started a forensics course at the high school. It was an interesting way to get kids to take more science and CSI was just heating up TV land. I had units on fingerprints, blood and blood spatter, metals and glass fragments and even tape and adhesive evidence. By far the most popular unit was the hair and fibers unit. There was something about getting out the microscopes and looking at different fibers and hairs that was fascinating to my students.
A good primer on hair evidence can be found at the US Department of Justice site.
Hair has identifiable patterns dependent on the animal and can be matched to the breed or animal type. Human hair has been studied even more extensively and can be matched to a specific person. This match is further reinforced using DNA. My students loved bringing in hair from their pets and seeing how those hairs differ from humans. There is a good site with lots of hair sample photos at the Microlab site.
This is a good time to bring in an unusual expert. I had several students whose mothers worked in hair salons. These women have an exceptional knowledge of hair characteristics and dyes. The photos and samples of dyed hair were the topic of conversation for weeks. One of the Moms even gave us a bit of a forensic lesson on how to tell if hair had been recently cut in microscopic photos.
In the Anthony case it is important to tell if hair samples in the trunk of the Anthony car were from someone who was living or someone who was deceased. Hair is a living part of our body and does change when we die. These changes can allow a forensic specialist to determine if the hair came from a living person or one who is deceased. When you think about it the only way a hair sample could be in a trunk that was shed from someone who was deceased would be a pretty big piece of evidence.
There is more on fibers and hair at the TruTV site. In fact, the site contains several chapters on forensics that would be helpful in any crime unit.
I love to use clips from TV shows in the forensic units but I caution you to carefully screen them for age appropriate materials. I would never use bloody or violent images with students. It is possible to make a point without the graphic photos or information. In fact property crimes, jewel heists, bank robberies; burglaries are much better subjects for study. The students will watch the gory TV shows and will want to talk about these crimes. That is generally OK as long as the crime does not involve a sexual assault. It is important to lay the groundwork clearly to all the students at the start of the unit.
So, with the high interest in this particular crime I will be watching and like any true teacher I will be looking for specific information and tools to use with my students so that the biology of hair, the physics of blood drops and the chemistry of solving crimes can help boost interest in the big ideas of science.