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Click here to see video of my crime lab tour!
| Crime Lab |
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| I am so excited to see how a REAL lab works! |
I love to watch crime shows on TV, and I thought that something about forensics would make an awesome experiment. This
is the Crime Lab I toured during my research. I met these investigators last year at my school's Science Olympiad. I e-mailed
one of the investigators with a lot of questions, and SHE INVITED ME TO COME AND TOUR THE LAB! It was amazing! I got to see
real forensic police at work.
I did a lot of research before I went to the lab. I thought it would be interesting to study how police spray special
chemicals to reveal latent blood at crime scenes. Latent blood is what is left behind after a criminal tries to clean up
the evidence. You can't see anything, but special sprays like Luminol and Bluestar will make bloodstains glow bright blue.
Then police can take a sample of the glowing blood spot and bring it back to the lab for more tests. This lab uses Luminol
for blood detection because they can make it themselves, which is very convenient.
While I was touring the lab, I learned that real police work is VERY different from TV. It seems like police are spraying
latent blood detectors every week on TV, but these police say they only use it a few times IN A YEAR!! The police demonstrated
how they use Luminol, and then they trained me how to use it. To work with Luminol, it has to be completely dark to see the
glow. If it is daytime, police have to cover up all the windows and doors with black plastic. This can take a long time
at a big crime scene. Luminol is sprayed on a surface, and if there is blood present there will be a blue glow that lasts
about 30 seconds.
| Can you spot the blood? |
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| Blood isn't always easy to identify! |
This is a t-shirt that is used for training police. Can you pick out the bloodstain?? (Hint: it isn't obvious) The stains
on the shirt are: A-1 Steak Sauce, Gatorade, pen, chocolate, blood and Kool-Aid.
The bloodstain is... #1 !!!! Are you surprised?? I was! Here are the rest: 2) A-1 Sauce, 3) red pen, 4) Gatorade,
5)chocolate
Your eyes can fool you, so that is why SCIENCE can give you the REAL answers!
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| Crime Lab Tour |
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| Ballistics Expert |
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At the lab, I got to see the investigators at work. It was INCREDIBLE!!! This officer showed me how they try to match bullets
from crime scenes to the bullets in the national police data base. I got to look at the room where they fire the suspect's
guns to capture the bullets for testing. There is a special tub filled with liquid, and they shoot the guns into it so they
don't blow a hole in the wall, or in somebody else! I learned that real police work is SLOW, and not fast like on tv. Did
you know that it really takes 3 weeks for DNA testing, and it is a GROUP of tests???
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| Taking samples from a stained t-shirt |
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A crime scene investigator and a lab technician showed me how to take samples of the stains on this shirt. At real crime
scenes, police take samples of all the evidence and then they bring it back to the lab. There is a special chemical that
can be added to samples that will cause a reaction if there is blood present. Then, the investigators look at the sample
under a microscope.
| Examining a sample under the microsope |
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| Crystals mean the sample is BLOOD |
When I added the special chemical to all of the samples from the stained t-shirt, only stain #1 grew crystals. This is the
scientific way to know that #1 is the only BLOODSTAIN! The latent blood detector sprays like Luminol are called "presumptive
tests" which means that a stain the glows COULD be blood. But, there are also other things that make blood detectors
glow, like metal, bleach and horseradish (huh?). So, a glowing sample basically means "run another test to make sure
it is blood." Once the stain passes the crystal test to confirm it is really blood, then the lab can run a DNA test.
A DNA test can match a tiny spot of blood to the person who left it there. Amazing!
| The Glow of Pennies with Luminol |
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| This is called a "False Positive" Reaction |
This picture is an example of the glow from Luminol when it is sprayed on pennies. This is called a "false positive"
reaction because the Luminol glows from something that is NOT blood. More tests are always needed to double check the glow.
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