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Formal Lab Report (science fair 2k16) Ms. Housen...

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How Sensitive is the Kastle-Meyer Blood Test?

Caroline Duncan

8th Grade

Bay Creek Middle School Ms. Housen

Introduction The Kastle-Meyer blood test is a tool commonly used by crime scene investigators and also popularly used on crime scene dramas. The test is used to test evidence that is believed to be blood to determine if the substance is blood or not. To perform this test, the evidence must be collected with a cotton swab and tested with a variety of chemicals. If the test detects blood the cotton swab will turn pink in a matter of 30 second, but if it does not trace blood, it will not turn any colors.The Kastle-Meyer test is proven to be a very reliable test, however the burning question is, will the Kastle-Meyer test be able to detect a miniscule amount of blood that has been heavily diluted?

Research There are many different ways to test for the presence of blood on objects. Crime Scene investigators use different methods in order to find traces of blood at a crime scene. One particular test is the Kastle-Meyer Blood Test. The history behind the creation of this test and procedure is one that was a long time in the making. The Kastle Meyer Test was established by Louis Jacques Thenard and Christian Friedrich Schonbein. They discovered that hydrogen peroxide is decomposed by blood and in 1863 they developed the first blood test based on that discovery. The KM (Kastle-Meyer) test is presumptive blood test, which means that the result of the test does not conclusively confirm or deny any presence of blood in the sample. The KM is a test that can detect blood by adding hydrogen peroxide to the blood sample and by doing this, it will cause the hemoglobin in the blood to try to decompose the peroxide when being exposed to

the blood. The hemoglobin does this because “The hemoglobin in the blood has a ‘peroxidase-like’ activity. Peroxidases are enzymes that break down organic compounds (hemoglobin), when combined with hydrogen peroxide (H2O2).” (Presumptive Blood Tests) This process is evident by the color change that will occur on the sample if it is positive for blood, which is because, “The KM test is all about transfer of electrons through reduction and oxidation (called redox for short). If something gains electrons, it is reduced, if something loses electrons it is oxidized. (Usually something gets oxidized when it reacts with oxygen, which is where the name comes from.) … Phenolphthalein is colorless when it’s reduced (has electrons), and pink when oxidized (no electrons).” (Sciencelineuscb.edu) Previously stated, the KM test is a presumptive test, meaning there are precautions that have to be made while using the test, to be cautious of false positive results. “Precautions: This test is presumptive because it has produced false positives from other substances, such as: saliva, pus, malt extract, vegetable extracts and salts of heavy metals.” (Forensic Resources) These false positives are triggered by chemical oxidants or vegetable peroxides. These false positives may only occur after the phenolphthalein was applied, because a true positive can only occur after the addition of the hydrogen peroxide. Thus, the KM test reacts to blood specifically. Because of these precautions, some may be asking why someone would use a test like this, especially when they could use another test that is more dependable. Well the reason for the use of this test is that it actually is quite reliable. “Sensitivity refers to the dilution factor of the substance that can not demonstrate the test. The sensitivity of the KM test is approximately 1:10,000: a drop of blood can still be detected so after dilution with 10,000 drops of water.” (Memim.com)

All information considered, if diluted the Kastle-Meyer blood test will still be able to detect presence of blood. Using this information given above and the hypothesis, an investigation will commence to test the factuality of the statement.

Hypothesis When increasing the amount of water to dilute a drop of blood, the Kastle-Meyer blood test will still present a positive result for the presence of blood.

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Experimental Design

Materials: -

Substances to test, including:

● Ketchup (1 bottle) ● Fresh Potato (1) ● Fresh Horseradish (1) ● Fresh Chicken (1 lb. or less - you only need the juice from the meat tray) ● Fresh Beef (1 lb. or less - you only need the juice from the meat tray)

● Paper plates (24)

● Permanent Marker (1) ● Disposable Gloves ● Knife or Vegetable Peeler ● Cutting Board ● Graduated Cylinder ● Eye Dropper ● Timer ● Lab notebook ● Water in a cup ● Kastle-Meyer kit ● Beaker

Safety Precautions: When working with chemicals and raw meat always make sure to wash your hands after use and keep the chemicals away from your eyes and mouth. Also keep the chemicals away from small children or animals. The chemicals and materials used in this investigation are not for consumption! Make sure to have adult supervision while doing this investigation. Even though you will not be dealing with any human blood, you should wear the appropriate protection, such as gloves. Raw chicken could have salmonella. Procedure: 1. Begin by researching the Kastle-Meyer procedure, and carefully read the instructions that accompany the kit.

2. The kit contains strips of paper that have been dipped in cow blood. These are the positive controls. 3. Using the permanent marker, label five plates, as follows: Ketchup, Potato, Horseradish, Chicken and Beef. You will also need to set aside another plate to do each test over (to catch any residue that drips off of the sample when testing). 4. Prepare each test substance, as described below a. For the potato, use a clean knife or vegetable peeler to cut a piece on a cutting board, then place the slice on the appropriately labeled paper plate. b. Repeat step 4a with a clean knife or vegetable peeler and cutting board for the horseradish. c. For the chicken and beef, pour a few drops from the container holding the fresh meat onto the appropriately labeled plate. Notes: Do not use all juice, as you will need more for the remaining two trials 5. Predict which of the test substances will test positive positive in the Kastle-Meyer test, and explain your reasoning in the data table 6. Following the directions that came with the kit, test each substance to see if it gives a positive Kastle-Meyer result. a. Take a cotton swab from the kit, and rub or dip it in the substance. b. Over the extra plate, add two drops of ethyl alcohol to the sample. c. Then (still over the plate) add two drops of the phenolphthalein to the sample.

d. After adding the Phenolphthalein to the sample, examine the sample for a color change (pink). If the sample changes colors after the phenolphthalein, you can conclude that it is a false positive. If the sample does not change colors, proceed to the next step! e. Add two drops (over the plate) of hydrogen peroxide to the sample. f. If you can see a color change (pink) within 30 seconds of the hydrogen peroxide being added to the sample, you can conclude you have a positive result. g. Record observations in lab notebook. h. Repeat the entire procedure, with clean materials, two times. Record your results. 7. If results are inconsistent (such as one positive and one negative for one substance in different trials), repeats the test carefully. Keep careful notes that might help explain inconsistent results. 8. To test the sensitivity of the test, get the beaker and graduated cylinder. Fill the graduated cylinder with 10 mL of water and pour it into the beaker. 9. Taking an eye dropper, add one drop of blood (from the beef meat tray) to the beaker of water. 10. Stir the blood in the beaker with an eye dropper. 11. Then take a cotton swab and dip it into the beaker and continue to test the sample for blood. 12. If the result comes out positive, add 10 more mL of water into the beaker. a. Continue to do steps 11 and 12 until you do not get a positive result. 13. Record observations and data in the lab book.

Data My initial predictions for each substance’s result from the Kastle-Meyer blood test:

Positive Results (predictions):

Negative results (predictions):

Beef Chicken

Ketchup Potato Horseradish

After being tested against the Kastle-Meyer blood test, these are the results for each substance in each trial: Substance

Ketchup

Chicken

Beef

Potato

Horseradish

Trial #1

Negative

Positive

Positive

Negative

Negative

Trial #2

Negative

Positive

Positive

Negative

Negative

Trial #3

Negative

Positive

Positive

Negative

Negative

Time it took to turn pink if positive

Never turned

7 seconds

1.5 seconds

Never turned

Never turned

The following table will be showing the data collected from the diluted blood tests. (Results are from diluted a single drop of blood in 10 mL of water, if the test presented a positive result 10 mL was added to the solution. This procedure was repeated until the result from the sample came out negative.):

Result from the test: Control- no reaction (negative)

Amount of water: 10 mL

Positive

10 mL

Positive

20 mL

Positive

30 mL

Positive

40 mL

Positive

50 mL

Positive

60 mL

Positive

70 mL

Positive

80 mL

Negative

90 mL

Negative

100 mL

Observations made during the dilution test: The pink color, due to the positive result, got lighter as the amount of dilution increased by 10 mL. At 90 mL there was no visible coloration.

Discussion

Conclusion T

Bibliography Helmstine, Anne Marie, Ph.D. "Kastle-Meyer Test To Detect Blood." About Education. N.p., n.d. Web. “Kastle-Meyer Test." MEMIM Encyclopedia . N.p., n.d. Web." "Serology - Blood and Other Bodily Fluids." Forensic Resources . N.p., n.d. Web. "UCSB Science Line." UCSB Science Line . N.p., n.d. Web. 25 Nov. 2016. "Presumptive." Wiley Encyclopedia of Forensic Science Jamieson/Forensic  (2009): n. pag. Web....