Forensic Escape Room: Design Your Own Biotech Adventure
Introduction Explore the world of forensic science with these fun and exciting escape room activities! Try forensic blood detection and agarose gel electrophoresis experiments, decipher clues, and solve puzzles. Learn to design your own escape room to have students unravel the evidence and free the innocent. Background Information Excerpts from EDVO-Kit 190 Crime scene analysts play a crucial role in collecting and preserving evidence, as contamination can compromise investigations. They identify materials such as blood, trace substances, and even skin cells under a victim’s nails to aid forensic analysis. Forensic scientists use various techniques to examine evidence, including presumptive tests , which indicate the presence of a substance, and confirmatory tests , which verify its identity. Microscopic and molecular analyses then compare evidence with potential suspects. Advancements in genetics have transformed forensic science, allowing DNA analysis from even tiny biological samples. Techniques like PCR and DNA fingerprinting help solve crimes and bring criminals to justice. FORENSIC SAMPLE ANALYSIS FOR BLOOD Blood is often found at crime scenes, in spatters, drops, and drips. Analyzing these spatters is a field of study in itself! Most blood spatter evidence is found around the victim or where the violence occurred. Blood itself can be found on clothes, skin, or in the get-away vehicle. However, a red stain on the floor at a crime scene can’t be immediately assumed to be human blood, nor can it be assumed to belong to the perpetrator. When something that is suspected to be blood is found at a crime scene, detectives will work quickly to secure the evidence and send it to a forensic lab for testing. Forensic scientists exercise caution before performing long, expensive DNA fingerprinting test on a sample that is not human blood. So, the first step when dealing with potential blood evidence is to confirm its human origin. This process begins with a simple presumptive test to distinguishes between blood and non-blood. Then, blood group typing is performed to confirm the sample is human and to help narrow down the suspects based on their blood group. The Kastle-Meyer test, introduced in 1903, is the most used presumptive test for detecting blood. It uses phenolphthalin and hydrogen peroxide to identify the presence of blood in samples. Phe- nolphthalin is a reduced form of the acid-base indicator phenolphthalein (Box 1). Phenolphthalein changes from clear to pink in basic solutions. When phenolphthalein in a basic solution gains two electrons, it shifts from pink to clear. This reduced molecule is used for the Kastle-Meyer test. To perform the test, the potential blood sample is collected on a cotton-tipped swab and then treated with a few drops of 95% ethanol to lyse, or break open, the cellular membranes. Next, phenolphthalin solution is applied, followed promptly by hydrogen peroxide. This sequence trig- gers a reaction where the iron in hemoglobin reacts with hydrogen peroxide, generating water BOX 1: Chemistry of the Kastle-Meyer Test The phenolphthalein (C 2 0H 16 O 4 ) used in the Kastle-Meyer test has been reduced, i.e. it has gained electrons, and is actually called phenolphthalin (C 2 0H 14 O 4 ) . The reaction in the Kastle-Meyer test is based on the reac- tion between the iron in hemoglobin and hydrogen peroxide (H 2 O 2 ). The iron in hemoglobin reduces (sup- plies electrons to) the H 2 O 2 , creating water (H 2 O). This reaction depletes the hemoglobin of electrons, which are in turn supplied by phenolphthalin. The oxidation, i.e. the release of electrons, of phenolphthalin turns it back into phenolphthalein, which has a characteristic pink color. Fe 4+ + C 2 0H 14 O 4 + H 2 O 2 → C 2 0H 16 O 4 + H 2 O + Fe 3+
2
Visit our website at www.edvotek.com
Made with FlippingBook flipbook maker