Presumptive Blood Tests
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What is a presumptive test?
A presumptive test in forensic science is a preliminary chemical screening test that indicates the possible presence of a substance, such as blood, drugs, or semen. These tests are sensitive but not specific, meaning a positive result suggests the substance might be present but doesn't confirm it, and further, more tests are required for definitive identification.
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Kastle Meyer Test
Use the Kastle Meyer test to determine which red stain is likely blood.
Next
Back
Click on each of the red stains to swab the area.
Sample 1
Sample 2
Sample 3
Sample 4
Next
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Click on the bottle of ethanol to add a drop to each swab. The alcohol will break open the red blood cells if they are present, exposing the hemoglobin.
Sample 1
Sample 2
Sample 3
Sample 4
Next
Back
Click on the bottle of Kastle Meyer reagent to add a drop to each swab. It includes an indicator called phenolphthalein in a potassium hydroxide solution.
Sample 1
Sample 2
Sample 3
Sample 4
Next
Back
Click on the bottle of hydrogen peroxide to add a drop to each swab.
Sample 1
Sample 2
Sample 3
Sample 4
Next
Back
Click view results to see the results of this test. If blood is present, the hemoglobin's iron component oxidizes the phenolphthalein back to its colored form causing a bright pink color to appear. Record which sample is likely blood on your lab sheet.
Sample 1
Sample 2
View Results
Sample 3
Sample 4
Next
Back
Watch the video to see how the Kastle Meyer test works in real life.
Next
Back
Hydrogen Peroxide
Use hydrogen peroxide to determine which red stain is likely blood.
Next
Back
Sample 1
Sample 2
Click on the bottle of hydrogen peroxide to add a drop to each sample.
Sample 3
Sample 4
Next
Back
Sample 1
Sample 2
Click view results to see the results of this test. Blood cells contain catalase which breaks down hydrogen peroxide into water and oxygen. If the stain is blood, you should see bubbling produced from the oxygen being released as catalase breaks down the hydrogen peroxide. Record which sample is likely blood on your lab sheet.
Sample 3
Sample 4
View Results
Next
Back
Watch the video to see how the hydrogen peroxide interacts with blood in real life. The blood being used in this video is pig blood.
Next
Back
Luminol
Use luminol to determine which red stain is likely blood.
Next
Back
Sample 1
Sample 2
Click the light bulb to turn off the lights!
Sample 3
Sample 4
Back
Sample 1
Sample 2
Click the spray bottle to spray luminol solution on each sample. If the sample glows blue, it indicates blood may be present. Record which sample is likely blood on your lab sheet.
Sample 3
Sample 4
Next
Back
Watch the video to see how the luminol interacts with blood in real life.
TRIGGER WARNING
In this video someone punctures their finger with a sharp object to obtain a blood sample to test with luminol. Feel free to skip this video if that of sort of thing bothers you.
Next
Back
ALL DONE!
Make sure you have answered all the questions on your lab sheet and hand it in!
Presumptive Blood Tests
Kimberly Mecir
Created on October 18, 2025
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Transcript
Presumptive Blood Tests
Begin
Back
What is a presumptive test?
A presumptive test in forensic science is a preliminary chemical screening test that indicates the possible presence of a substance, such as blood, drugs, or semen. These tests are sensitive but not specific, meaning a positive result suggests the substance might be present but doesn't confirm it, and further, more tests are required for definitive identification.
Next
Back
Kastle Meyer Test
Use the Kastle Meyer test to determine which red stain is likely blood.
Next
Back
Click on each of the red stains to swab the area.
Sample 1
Sample 2
Sample 3
Sample 4
Next
Back
Click on the bottle of ethanol to add a drop to each swab. The alcohol will break open the red blood cells if they are present, exposing the hemoglobin.
Sample 1
Sample 2
Sample 3
Sample 4
Next
Back
Click on the bottle of Kastle Meyer reagent to add a drop to each swab. It includes an indicator called phenolphthalein in a potassium hydroxide solution.
Sample 1
Sample 2
Sample 3
Sample 4
Next
Back
Click on the bottle of hydrogen peroxide to add a drop to each swab.
Sample 1
Sample 2
Sample 3
Sample 4
Next
Back
Click view results to see the results of this test. If blood is present, the hemoglobin's iron component oxidizes the phenolphthalein back to its colored form causing a bright pink color to appear. Record which sample is likely blood on your lab sheet.
Sample 1
Sample 2
View Results
Sample 3
Sample 4
Next
Back
Watch the video to see how the Kastle Meyer test works in real life.
Next
Back
Hydrogen Peroxide
Use hydrogen peroxide to determine which red stain is likely blood.
Next
Back
Sample 1
Sample 2
Click on the bottle of hydrogen peroxide to add a drop to each sample.
Sample 3
Sample 4
Next
Back
Sample 1
Sample 2
Click view results to see the results of this test. Blood cells contain catalase which breaks down hydrogen peroxide into water and oxygen. If the stain is blood, you should see bubbling produced from the oxygen being released as catalase breaks down the hydrogen peroxide. Record which sample is likely blood on your lab sheet.
Sample 3
Sample 4
View Results
Next
Back
Watch the video to see how the hydrogen peroxide interacts with blood in real life. The blood being used in this video is pig blood.
Next
Back
Luminol
Use luminol to determine which red stain is likely blood.
Next
Back
Sample 1
Sample 2
Click the light bulb to turn off the lights!
Sample 3
Sample 4
Back
Sample 1
Sample 2
Click the spray bottle to spray luminol solution on each sample. If the sample glows blue, it indicates blood may be present. Record which sample is likely blood on your lab sheet.
Sample 3
Sample 4
Next
Back
Watch the video to see how the luminol interacts with blood in real life.
TRIGGER WARNING
In this video someone punctures their finger with a sharp object to obtain a blood sample to test with luminol. Feel free to skip this video if that of sort of thing bothers you.
Next
Back
ALL DONE!
Make sure you have answered all the questions on your lab sheet and hand it in!