Crime Scene Science: Solving Mysteries by Investigating Blood Stains
Do you enjoy watching mysteries or crime investigation shows? Every criminal leaves behind evidence at the crime scene. The trick to catching the criminal is collecting all of the evidence and making sense of it. This is what a forensic expert does. In this bloody, Halloween-themed science activity you’ll be correlating the size of blood stains to the distance they fell, but don’t get too grossed out; you’ll be doing it with fake blood. If you like figuring out mysteries, this is the activity for you!
This activity is not appropriate for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.
Forensic science is any science that is used in the courtroom or judicial system and it is extremely vital. The goal of a forensic scientist is to remain impartial and to appraise all of the available evidence in order to determine the truth. Forensic science includes many areas of study, such as criminalistics, engineering science and pathology and biology. For example, if a sports player were to die suddenly while playing a game, a forensic scientist with a specialty in pathology and biology would be called in to find out the cause.
In crime scenes where people are wounded, investigators apply principles of blood spatter analysis by taking measurements, such as of the diameter of the blood spatter (drops), to figure out what happened. How do you think the diameter of spatter changes as blood is dropped from different heights? Find out by using some fake blood in this activity and trying your hand at collecting evidence!
Extra: Instead of dropping the fake blood straight down, try dropping it at angles to the ground, or dropping it while moving the dropper in a certain direction. Be sure to do this in a location that can be accidentally stained with fake blood! How does this change the size and shape of the drop’s impact and where the spatter ends up?
Extra: Repeat this activity over other surfaces, such as newspaper, printer paper, parchment paper, paper towels, butcher paper, or wood. How do your results change when using different surfaces?
Extra: In this activity you tried dropping fake blood from one, three and five feet. Try repeating the activity but use different heights (such as two, four, six and seven feet) and then graph your results. What kind of graph does the data make? What kind of mathematical correlation is there between the height the drop is dropped from and its diameter on the surface it lands on?
Observations and Results
You should have seen that the drops made from dropping the fake blood at five feet were the largest in diameter, while the drops made from dropping the fake blood at one foot were the smallest in diameter. However, the differences in diameters were likely small, with the five-foot drops possibly being about 12 millimeters (mm) in diameter, the one-foot drops being about 10 mm in diameter, and the three-foot drops being in between at about 11 mm in diameter. By understanding how blood spatter increases in diameter as the dropping height is increased, forensic scientists can better figure out what happened at some crime scenes where people are wounded.
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Teisha Rowland, PhD, Science Buddies
Science Buddies |
Crime scene investigation, forensics, solving mysteries, models
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