Body Fluids

Trace Evidence


Physical Properties- The Average adult has a blood volume of approximately 5 liters, which composes about 8% of the body's weight. Plasma constitutes approximately 55% of blood's volume. It is estimated that plasma may contain as many as 40,000 different proteins from about 500 gene products. Approximately 1,000 proteins have been detected.

Chemical Properties- Blood is one of the best things for investigators to find at a crime scene. Blood can distinguish if a person has any kind of sickness or disease that could narrow down to a smaller group. Furthermore when it comes to blood this is the best evidence because it classifies a person directly rather than classifying a group. The blood contains DNA which is unique to every individual having unique chromosomes from each parent. In simple sampling a doctor could see a type of blood, those blood types being (a+,a-, b+, b-, ab+, ab-, o+, and o-)

How Forensic Scientist Analyze- The first step to analyzing blood is to figure out what the blood type is and if it is even human. The Blood is then sent to a lab. The test is done using two solutions each containing antibodies to type A and type B blood antigens. The first solution contains type A antibodies and when mixed with type A blood, will cause it to form clumps. The same concept is used for testing type B blood. When there are type B antigens, the solution of type B antibodies would cause all the B antigens to clump. If the blood clumps are under contact with both A and B antibodies, then it is the blood type AB since both antigens are present. O blood does not clump with any other blood type and is identified because it is solitary.


Physical Properties- The physical properties of sweat are water and salt.

Chemical Properties- Sweat is mainly salt and water. This comes from excessive exercise or movement also it can come from extremely hot weather. Sweat is secreted from the sweat gland. The two types sweat glands in the body are endocrine and apocrine. The importance of sweat at a crime scene is that it contains DNA and the salt is in sweat is more susceptible to preserve a fingerprint or any other kind of evidence that could help solve a case.

How Forensic Scientist Analyze- For the longest time fingerprints were the gold standard for linking suspects to crimes. Today though DNA is the ultimate way to collar a suspect. Even criminals being extra careful will most likely leave DNA. All it takes is a few cells to obtain enough DNA information to identify a suspect to near certainty. A drop of sweat can be taken off the inside of a baseball cap can ID the suspect. The baseball cap will be sent to the lab to a DNA expert. They will extract the sweat and run the DNA to find the suspect.


Physical Properties- Vomiting is the forceful discharge of gastric contents, may be a protective physiologic mechanism that prevents entry of potentially harmful substances into the gastrointestinal tract. Vomit consist of food previously eaten and stomach bile. Bile comes from the small intestines which helps neutralize stomach acid. Bile contains a person's DNA.

Chemical Properties- Within vomit there is more than just digested food there is bile. Bile contains DNA which can help identify the victim. But if the identity of the person is already known, an investigator can approximately identify what and even where the person had eaten before. They can follow the person’s path from there and possibly get an identity on the person. This makes it easier for investigators to connect or find a person.

How Forensic Scientist Analyze- When the investigators find vomit at a crime scene they send it to the lab, because in vomit there is bile, and in bile there is DNA. The bile is then processed and the genetic code is recorded.

Case Study

Blood Spatter Proves Teen Did Not Murder Her Parents

Sarah Johnson, 18, who faces life in prison for two counts of first-degree murder, did not have her parents' blood on her that morning. The defense claimed that the close-range shots that killed Diane Johnson would have projected a significant amount of blood at the shooter, who was standing no more than a foot away from the victim. Sarah Johnson did not have any blood on her that morning. The only blood that was found was on Sarah's bath robe, which the killer was wearing, but there is no proof that Sarah was wearing it that morning. The blood splatter in the room and the lack of blood on Sarah proves that she could not be the killer. This is a case were the bodily fluid, blood was used to solve a murder case.

How DNA Testing works

Works Cited

Works Cited

"Blood Basics." Sigma-Aldrich. N.p., n.d. Web. 5 Feb. 2014. <>.

"Forensic Science | Blood Analysis." ThinkQuest. Oracle Foundation, n.d. Web. 5 Feb. 2014. <>.

"How DNA Testing works." YouTube. YouTube, 20 Oct. 2012. Web. 5 Feb. 2014. <>.

"Nausea and Vomiting." Nausea and Vomiting. N.p., n.d. Web. 5 Feb. 2014. <>.

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