Monthly Archives: April 2016

Spatter not splatter

Blood spatter analysis is an interpretation of blood stains in order to recreate what caused the bloodshed. It uses size, shape, location and distribution in order to trace it back. 

This graphs shows the comparison of the height from which a blood drop is dropped from and the diameter of the drop. A trend we see is that a higher height leads to a bigger diameter. We did see the same results as the “conventional wisdom” that the higher the height the larger the diameter. Because of the Height of the blood droplet the greater the acceleration is due to the force of gravity therefore making the impact larger and the diameter larger as well. We found an equation that could lead to our findings which is Y= .025X + 1.16

My second graph is a comparison between width&Length and Angle of the blood drop. A trend we see is that if we have a larger angle we will receive a larger width&length. We found an equation for this graph as well which is Y= -0.125X + 1.10 

In order to determine the direction from which the blood drop originated you have to trace back  by drawing a vertical line through the middle of the blood spatter to the tail. In order to determine the point of impact you just have to trace all the tails from your blood stains and once you have a point where all the lines meet, you have your point. Direction and convergence are important because it can show where someone was when they began bleeding and to trace back the suspects “footsteps.” 

I learned that a few simple drops of blood are able to tell an entire story of a crime scene just by location, shape, size and distribution of them. The only question I have is if blood spatter analysis has ever been wrong before. 

The Case of the Bicycle Burgler

Well, Joe and I collected soil then we use forensic techniques with soap and water in order to get the soil we found separated into sand, silt and clay. After a comparison of the soil that the police had given us, we found the criminal who stole the bike.

The purpose of this investigation is to show how soil can be used in forensics investigations and catch dangerous criminals. Last week Joe and I went to the front of the school and collected 2 soil samples, 1 next to the building itself and the other across in this patch of sandy near the parking lot. We used both soils and compared them to the soil that the police found and determine where the bike was.

Soil is important to forensics investigations because certain soil can be found in specific areas linking things and people to crime scenes. The 4 major soil categories are sand, clay, silt and loam. You can determine the type or texture of soil using the texture triangle. Chemical tests can tell you the percentages of how much sand, clay and/or silt is in the type of soil.

 Our soil we collected is labeled “My soil” and the crime scene soil is labeled “C.S.” Visually the soils are different in color and in the amount of rocks. Our soil felt more sand like and the crime scene soil felt more like dirt.

 This is a soil texture triangle. It shows how much of what soil is in it and what type of texture it is. The blue dot is the crime scene while the red dot is the soil we collected. These textures are not similar. Therefore the soil samples are not the same.

 This is our chemical comparison table that compares the pH level and the texture of the 2 soils. In the sense of the pH the soils do match, both being at an 8 level. However the texture of the soils are not a match.

In conclusion, our soil did not match with the soil found at the crime scene. However we did find the same soil on the shoes of a student by the name of Jacob Limon. I learned that soil actually plays a big part of forensics investigations due to the fact that it can link people to a crime scene. I also learned that Jacob is a criminal. The only question that i have about the soil analysis is why the pH levels matched. The next step of the investigation should be to hunt down Jacob Limon, arrest him and prosecute him to the fullest extent of the Law!