2. Bloody Remains: Fireflies and crime scenes

3. Blood and Crime blood When you think about a crime, you usually visualize bloody walls, floor, and maybe even ceilings. So, let’s discuss how crime scene investigators determine the events of a crime—when there’s no blood to be seen.

8. What is luminol? A chemical used by forensic investigators to detect latent (hidden) traces of blood. Luminol Synthesis:

9. What does luminol do? Reacts with hemoglobin and produces light –Fe ++ in hemoglobin is a catalyst for the reaction –This is why it detects bloodstains Emits light photons by chemiluminescence –Common example: Fireflies (bioluminescence) and light sticks

10. What is chemiluminescence? Chemiluminescence is the emission of light during a chemical reaction. A molecule that is chemiluminescent is oxidized in a chemical reaction to an excited state product and emits light upon deexcitation. Luminol is a chemiluminescent molecule which was discovered by the German scientist H.O. Albrecht in 1928. It has been used in many chemical applications because of its chemiluminescent properties.

12. Applications A basic luminol solution combined with hydrogen peroxide and a thickening agent can be sprayed on surfaces with suspected blood traces. The solution will glow if catalyzed by the presence of a metal ion, such as iron in blood hemoglobin. Disadvantage –Luminol can be catalyzed by substances such as bleach, copper, potassium permanganate (found in many dyes), saliva, brain tissue, bone marrow, rust, and vegetable enzymes. –Secondly, luminol can destroy some genetic markers in cell DNA. –Thirdly, it can smear bloody impressions and make prints and spatters more difficult to analyze.

13. How and when is it used? Requirements: darkness (block windows) Interestingly, luminol has the potential to destroy other valuable evidence at a crime scene. For this reason, investigators attempt to determine events of a crime and identify evidence using other methods before using luminol.

14. The forensic use of luminol chemiluminescence to detect traces of blood inside motor vehicles By: T. I. Quickenden, C. P. Ennis, and J. I. Creamer Research Article

15. Table 1: Interference Tests

16. Table 2: Post-Cleaning Intensity

17. What’s the better deal? Soap and water and cleaners produced better results than plain water because they have the ability to bond to both the uncharged main cage of hemoglobin and the charged ferrous iron center. Water on the other hand, only interacts with the charged center.

18. Cleaning Effects Picture a circle that has been exposed to blood. If the blood has been treated with luminol and glows at 100 then a small portion of the circle has been washed with water. The washed part will glow at best about 50% less than the unwashed part. The same circle washed with a soapy water or a cleaner would show a reduced chemiluminescence intensity of about 10% of the unwashed portion.

19. Research Article Supplement Attempted cleaning of bloodstains and its effect on the forensic luminol test By: Jonathan I. Creamer, Terence I. Quickenden, Leah B. Crichton, Patrick Robertson, and Rasha A. Ruhayel

20. Figure 1: Water Cleaning Effects Wet blood washed off better. Dried blood proved to be more difficult.

21. Figure 2: Bleach Cleaning Effects Again, wet blood came off better. However, bleach became the agent of interference.

22. Table 1: Drying Times Over time, interference from the bleach became negligible because the stabilizers in bleach decompose quickly.

23. Conclusions Roof linings, trunk linings and carpets allow blood to soak into them, thus, it is hard to remove completely. Carpets have a bigger surface area. Advantage: it holds the blood longer Disadvantage: luminol may not pick it up if it’s been washed

24. Conclusions Cont. Wet blood washes off better than dried blood. Certain things can serve as an interfering agent. Bleach produces a false positive in the luminol test because of its components but over time, it becomes negligible.

25. Implications Luminol is a useful tool used to detect bloodstains at crime scenes Clean up the blood with soap and water or a cleaner before it dries, but know that it doesn’t always eliminate bloodstains. Also, steer clear of bleach.

26. Just Kidding For your health and everyone else’s, please refrain from murder.

27. Ok, now seriously… The use of luminol in forensic investigations has proven tried and true for many years. Though some materials interfere with it, surprisingly, it does a good job in identifying very old, dried blood.