1.1.4. Blood Evidence

What does blood do?

- Delivers oxygen & nutrients & water & hormones to cells - Carriers away waste - Fights infections - Stops bleeding (when cut/bruised)

Is human blood ever blue? What other colors can blood be?

Blood can be dark blue, a pinkish violet color, and green.

Leukocrystal Violet

LCV reacts with hemoglobin and turns a violet color. Usually used on porous surfaces, such as a large stain on a carpet, LCV is not the best to use in the lab.

Luminol

Luminol glows bright blue in the dark when it comes in contact with blood. However many other substances will cause it to react, so it is not the best test to use in the laboratory.

Kastle-Meyer

Most common test. This test uses a compound known as phenolphthalein, which reacts with the iron carried by hemoglobin. This test will be used in the lab.

Describe what presumptive and confirmatory tests indicate about possible blood samples, and explain why you will perform both tests on the samples from the scene.

Presumptive tests determine whether the blood sample is blood or not, and confirmatory tests confirm if the sample is blood. We perform the presumptive test to see if there's a possibility of blood and then we perform the confirmatory test to identify if a sample is actually positive.

Confirmatory Testing

Relies on other unique properties of blood, such as the proteins present on the surface of red blood cells called *antigens*. These tests confirm the presence of blood at the scene.

How to Remove Gloves

1. Grasp the outside edge of the glove 2 Peel the glove away from your hand turning it inside out making sure the contaminated side is on the inside 3.Hold on to the discarded glove with your left hand 4. Slide your ungloved finger under the remaining glove and peel the glove off from the inside. 5. It will create a little bag for both of the gloves. 6. Then throw it away

Platelets (Leukocytes)

A minute, colorless, anucleate disk-like body of mammalian blood that assists in blood clotting by adhering to other platelets and damaged epithelium.

Red Blood Cells (Erythrocytes)

Hemoglobin-rich, red blood cells that transport oxygen through the body. Erythrocytes give the red color to vertebrate blood and do not have nuclei.

Negative Controls

In an experiment, the group in which the conditions produce a negative outcome. Negative control groups help identify outside influences that were not accounted for when the procedure was created.

Positive Controls

In an experiment, the group that the researcher expects to have a positive result, shows that the experimental setup was capable of producing results.

Is human blood ever blue?

No, human blood will always be red no matter what circumstances.

White Blood Cells (Thrombocyte)

One of the many cells in the blood that lack hemoglobin but have a nucleus and are active in the immune response. Lymphocytes, monocytes, neutrophils, eosinophils, and basophils are leukocytes.

Did the samples from the scene test positive for blood? If so, can you be certain from this test that the samples are in fact blood?

Only two of the samples tested positive for blood. No, because this test isn't a hundred percent it can tell you a sample is positive but it'll be negative.

Presumptive Testing

The initial testing suggests a sample may be blood. These tests identify blood-based on the properties of *hemoglobin*.

Plasma

The pale yellow, liquid portion of blood consists of water and dissolved substances, including sugars, lipids, metabolic waste products, amino acids, hormones, and vitamins.

What's in blood?

plasma, red blood cells, white blood cells, platelets