CLASS COPY DO NOT REMOVE FROM ROOM



CLASS COPY DO NOT REMOVE FROM ROOM!

THE MYSTERY OF THE BLOODY STAIN

OBJECTIVES

o Perform a test to determine if the stain is blood

o Determine the ABO Blood type of unknown blood samples

o Identify which of the three suspects is most likely to have committed the crime

BACKGROUND

Blood and blood stains left behind in a crime scene are important evidence and provide crucial information in a criminal investigation. Blood evidence is usually used to exclude someone as a suspect, narrowing the list of possible suspects. Forensic scientists look at specific proteins (A, B and Rh) on the red blood cells and determine the type of an unknown blood sample based upon their presence.

Blood is a tissue comprised of four components: red blood cells, white blood cells, platelets and the liquid portion of the blood called plasma.

One of the preliminary tests for crime investigators is to determine if a suspicious stain is blood. This is done by treating the stain with Luminol, which glows under UV light if blood is present. The Luminol is reaction with the iron in the hemoglobin on the red blood cells.

DETERMINING THE ABO-RH BLOOD TYPE OF SIMULATED BLOOD SAMPLES

There are surface proteins on the red blood cells that determine an individual’s blood type. These surface proteins are called antigens. Dr. Karl Landsteiner received the Nobel Peace Prize in 1930 for his work on blood typing.

Since the antigens present on the surface of a red blood cell determine the blood type, an individual with A antigens has A blood type. One with B antigens has B blood type, and one with both A and B, has AB blood type. A person with no antigens has O blood type.

Plasma has circulating proteins called Antibodies. For example, if a person has A antigens, they have B antibodies; those with B antigens have A antibodies, and those with A and B antigens have no antibodies. People with no antigens have both A and B antibodies

Data Table 1: ABO Blood types Summary

|Blood Type |Antigen on |Antibodies in |Can Receive Blood From |Can Donate Blood to |

| |Red Blood Cell |Plasma | | |

|A |A |B |O,A |A,AB |

|B |B |A |O,B |B,AB |

|AB |AB |none |O,AB,A,B |AB |

|O |none |A and B |O |O,A.B.AB |

Data Table 2: Agglutination (clumping) Reactions in ABO System

| | | | |

|Blood Type |Anti-A Serum |Anti-B Serum | | |

|A |Agglutination |No Agglutination | | |

|B |No Agglutination |Agglutination | | |

|AB |Agglutination |Agglutination | | |

|O |No Agglutination |No Agglutination | | |

Another Important antigen on the surface on the red blood cell is the Rh protein, named for the Rhesus monkey in which it was first studied. People who have this protein are Rh- positive and those who lack it are Rh-negative.

Data Table 3: Rh Agglutination Reactions

|Rh Agglutination Reaction |Rh Factor |

|Agglutination |+ |

|No Agglutination |- |

Data Table 4: Frequency of ABO Blood Types and Rh in the U.S.

|Blood Type |Frequency Percentage|

|A |42 |

|B |10 |

|AB |4 |

|O |44 |

|Rh+ |85 |

|Rh- |15 |

Name:______________________________

Blood Typing Lab: Crime Scene Scenario

Last night someone broke into a jewelry store. A team of crime scene investigators were called to the scene of the burglary. Upon arrival the CSI’s noticed that several glass display cases were smashed, scattering glass throughout the store. A closer examination of the glass fragments revealed small pieces of what appeared to be blood stain clothing were left behind. The clothing pieces were carefully collected and sent to the forensics lab for analysis. Based on the evidence, the CSI’s apprehended three suspects. Since select red colored stains may look like blood, forensic scientists must first determine if the red stain is actually blood. A test is performed to determine the presence of blood components such as hemoglobin was done on the blood. Due to the positive results and the presence of white blood cells, it was determined to be human blood. The blood will now need to be blood typed. Your jobs as a forensic scientist is to provide crime investigators with additional proof in order to determine which of the suspects may have committed the burglary. You will type the blood samples found at the crime scene to match the samples drawn from the three suspects.

Activity One: ABO and Rh Blood Typing

Once it is verified that a stain is indeed blood, a sample is carefully collected and taken to a forensics lab. The next test on the blood sample, collected at the crime scene is to compare it to blood types of the three apprehended suspects.

Materials:

← Procedures:

Place 2 drops of the simulated blood sample in each well of the blood typing tray for each sample: 1. Crime Scene and Suspects 1-3

a. You will have separate trays for each blood sample

2. Place 2 drops of Anti-A Serum in well A.

3. Place 2 drops of Anti-B Serum in well B.

4. Place 2 drops of Anti-Rh Serum in well Rh.

5. Use a separate stick to mix the samples and each serum for 10 seconds each.

Carefully examine each well to determine if there is any change and record results into chart

If it is a positive reaction, the blood will agglutinate (CLUMP)

A change in overall color is also considered a positive reaction

Clean up: Thoroughly wash and dry all trays and sticks, before you return them to their bags.

|Simulated Blood Sample |Agglutination in Well A (+/-) |Agglutination in Well B |Agglutination in Well Rh |Blood Type |Observations |

| | |(+/-) |(+/-) | | |

|Crime Scene | | | | | |

|Suspect 1 | | | | | |

|Suspect 2 | | | | | |

|Suspect 3 | | | | | |

Understanding your Results (Analysis)

Clumping indicates that the blood sample contains antigens that reacted against antibodies in the typing serum that you mixed it with.

Questions to answer…in complete sentences on separate piece of paper. Please staple to this page and hand in.

1. What are the four major components of blood?

2. Why is it important to make sure you get the right kind of blood?

3. What does the presence of red and white blood cells in a sample indicate?

4. Why does the presence of hemoglobin provide proof that the stain is actually blood?

5. What is the purpose of the hemoglobin on red blood cells?

6. What is an antigen and where are they found?

7. What is an antibody and where are they found? Be specific!

8. What is agglutination?

9. What does agglutination tell us?

10. Based on your results, which suspects blood type matches the crime scene blood?

11. Based on your results, do you think there is enough evidence to prove the suspect committed the

burglary?

12. Choose one of the following topics: Write a Summary of Learning (1/2 page) and please print the article and attach it to this lab report.

A. Research how Blood typing can be used in paternity cases

B. Research how blood evidence is collected at crime scenes

C. Research how blood found at a crime scene is distinguished as animal or human blood.

DON’T FORGET TO ATTACH THE ARTICLE

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Negativeeeee

Positive

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