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Transcript of Anna's Garcia
Blood spatter analysis is one of the several specialties in the field of forensic science. It is the examination of the shapes, locations, and distribution patterns of blood stains in order to provide an interpretation of the physical events that took place at the crime scene. “Blood can be a very powerful form of evidence. (1. 1. 6: Blood Spatter Analysis PLTW resource sheet)
Blood type and DNA evidence provide crucial pieces of information but bloodstain patterns left at a crime scene can also be very useful as they can help investigators establish the events that took place during the crime.”(Project 1.1.6: Blood Splatter Analysis PLTW packet)
The practice is based around the idea that blood will follow the rules of physics, as they would apply to liquids (Forensic Science Central, n. d.).
The category of blood spatter we will be focusing on is low-velocity. These are usually the result of dripping. Those spatters usually have a force of impact of 5fps (feet per second) with a diameter ranging from 4 to 8mm. Low-velocity spatters often occur after the initial injury is sustained. They also result in pools of blood around the victim and smears or trails (How Stuff Works, n. d.).
The victim in this case is Anna Garcia. Miss Garcia is a young, recently divorced woman who co-owns a bakery with her friend and business partner, Lucy Leffingwell. She was found dead, face down in her kitchen with the front door locked and pet dog next to her. She had vomited oatmeal and the table had been knocked over. There was a pool of blood near her head and spatters on the table, the window, and the dog’s tail. There was also an open, spilled-over bottle of prescribed aspirin in the living room. She had also recently ended a relationship with her neighbor, Doug Greene, who called the police.
The entire purpose of doing a blood spatter analysis on Anna Garcia is to see from what height she fell from by running a controlled experiment where we know the exact height each drop of blood is falling from and comparing the results to the diameters of the spatter from the crime scene.
First, we covered the floor with plain copy paper and taped it.
Then, we took 2-3 trash bags and covered the wall and taped it.
Next, use mask and measuring tape to mark on the garbage bags at every 2o centimeters; starting at 0 cm and finishing at 200 cm.
After that, we filled a miniature beaker with 30ml of water and added one drop of blue food coloring dye, we gave it a few seconds for the dye to diffuse.
Then, we began our control test. We took the blue dye and with the pipette we dropped accurately from each marking, and with the help of a ruler to keep it equal and steady, we then collected our data from our control and wrote the diameter next to the drops on the paper.
Finally, we started the experimental test. Using the simulated blood, rulers, and a pipette we dropped a droplet from every 20 cm until we reached 200 cm. We did two trials of this and collected all of our data and put it into a line graph.
How Data Was Kept and Recorded
Made a line graph
Graphed the measurements according to the relationship between diameter and height
Y-axis labeled: Diameter of Blood Spatter (in cm)
X-axis is labeled: Height Dropped From (in cm)
Anna Garcia fell from 175.26 cm (5 ft. and 9 in.)
The diameter of Anna's blood is around 1 cm
The blood dropped from 180 cm was the closest in diameter at 1.1 cm.
The results of our experiment show that as the drop height increased, the diameter increased in some cases. However, it was still quite varied. The diameter would increase some of the time, and stayed within a certain range as the drop got higher, but it would vary from higher to lower than the previous drop. It did not increase every time. The diameter also did not increase higher than 3 cm.
A. Test 1- Control Group
For the control test we dropped our blue food coloring dye mixed in water from each height, counted by 20s and used centimeters for our measurement, and found that the higher we dropped the mixture, the wider the diameter became. We came to the conclusion that with this experiment that the more high up we drop the drops, the wider the diameter gets.
B. Test 2- Experimental Group 1
For this experiment we dropped the blood with the pipette from each height and found that the diameter increases as the height does but it does not increase as much as the control group did.
C. Test 3- Experimental Group 2
For this experiment we followed the same procedure as the first experimental group. However this time we had already done the experimental procedures twice and had become more proficient so we went faster and with a bit more ease. When the results lined up with the results from the previous trials we were able to confirm the type of velocity the crime scene spatter was and the approximate height from which the blood at the crime scene fell.
If we run an experimental test where we know what height we dropped each droplet of simulated blood from, then we will be able to determine what height she fell from by comparing the diameters of her blood spatters and our experimental spatters.
Wear Goggles-keep testing liquids out of eyes
Wear Gloves-protect hands from testing liquids
Keep Hair out of Face-do not get simulated blood or any other substances in your hair
Cover the Walls-keep the area protected from the blood spatter
A large quantity of white copy paper
2-3 garbage bags
Blue food coloring
If Anna Garcia fell from her full height, which is 5 feet and 4 inches tall, then the blood spatters would be low-velocity.
1. Rankin, S. (n. d.). Bloodstain Pattern Analysis. Forensic Science Central. Retrieved from forensicsciencecentral.co.uk/bloodstains.shtml
2. Project 1. 1. 6: Blood Spatter Analysis PLTW resource sheet
3. Freeman, S. (n. d.). Blood Spatter.
How Stuff Works
. Retrieved from http://science.howstuffworks.com/bloodstain-pattern-analysis2.htm