1. The greater the height, the greater the speed of the blood upon impact and hence the larger the diameter of the blood stain.
2. Instructions from Ms Siow (latest)
2.1. This Mindmap is private (editing rights), however, you can share this mindmap with anyone. You may wish to also share with your rgs.edu.sg account on mindmeister.
2.1.1. Do not share with others who will not contribute to the mindmap
2.2. In groups of 6, choose one of the following node to summarize on the topic. The others can read the Google Site on CSI, and only one laptop may be used to edit this mindmap
2.2.1. You are reminded to make small changes, and click refresh to ensure that it is saved
2.2.2. Once the team is happy with the changes, to play safe, you may wish to Export your mindmap. Click the arrow below, then export
2.3. For groups who are faster, you may also make use of this lesson to update your e-journals
2.4. HOW TO USE
2.4.1. 1) Click + to add new sub-node. 2) Click on node and delete on keyboard to delete node. 3) You may also add in files such as images, add links, and add notes to this mindmap by clicking Properties at the right side
2.5. Feedback on USE OF MINDMEISTER Please add here.
2.5.1. (Do not DELETE, else... ) it is possible to track which group edited !!!!
2.6. IF you are using a public computer, please REMEMBER TO LOG OFF. Click My Maps on Left Hand Side, then log off
3. Blood Identification Talia, Lexxis, Christal, Zeph, Jemi, Vernis. (15, 13, 23, 12, 17, 26
3.1. Luminol
3.1.1. Steps
3.1.1.1. Step 1. Drip one drop of sample onto the filter paper
3.1.1.2. Step 2: Go into a dark area
3.1.1.3. Step 3. Spray laminal solution onto the filter paper
3.1.1.4. Step 4. Observe for a blue glow. http://www.theage.com.au/ffximage/2006/07/09/9n_blood_wideweb__470x304,0.jpg
3.1.2. Advantages and disadvantages
3.1.2.1. Advantages
3.1.2.1.1. Results (blue glow) can be obviously seen with the naked eye
3.1.2.2. Disadvantages
3.1.2.2.1. The glow can only be seen for about 30 seconds hence, it cannot be a permanent evidence.
3.1.2.2.2. Luminol can be triggered by a number of other substances such as copper or even bleach. Hence, it can only be used as a presumptive test.
3.1.3. Other information
3.1.3.1. The catalytic activity of the heme group accelerates the oxidation of the laminal, producing a blue-white to yellowish green light where blood is present
3.1.3.1.1. Why?The luminol goes through a chemical reaction with haemoglobin and the reactants have more energy than the products. hence, the molecules get rid of the extra energy in the form of visible light photons
3.2. CATALYTIC TEST
3.2.1. WHY
3.2.1.1. Hydrogen peroxide will react with the catalase to break down H2O2 into H2O and O2, releasing the O2 in the form of bubbles
3.2.2. Steps
3.2.2.1. STEP 1: Drip two drop of sample onto the rag.
3.2.2.2. Step 2:Drip one drop of ethanol onto the same hole of the rag
3.2.2.3. STEP 3: Drip 2 drops of hydrogen peroxide
3.2.3. Advantages and disadvantages
3.2.3.1. advantages
3.2.3.1.1. New node
3.2.3.2. disadvantages
3.2.3.2.1. False results in the presence of vegetables peroxidases such as those in broccoli, cauliflower and etc.
3.2.3.2.2. Will react with non-human, hemoglobin-base blood. That means we cannot tell if it is human blood
3.2.3.2.3. Only a presumptive test
3.3. Kastle-Meyer Reagent (Reduce phenolphthalein kept in alkaline solution in the presence of zinc) Colour change: Colourless reagent will turn pink. This is indicative of the presence of haemoglobin.
3.3.1. Pros and Cons
3.3.1.1. Chemical oxidants such as copper and nickel salts will cause the Kastle-Meyer reagent to turn pink before the addition of the hydrogen peroxide.
3.3.1.2. The test will give a false positive result when in the presence of vegetable peroxidases, such as those in horseradish, BROCCOLI , cauliflower, etc and chemical oxidants other than blood.
3.3.1.3. Test is not conclusive as it is merely a presumptive test.
3.3.1.4. The Kastle-Meyer test has the same reaction with human blood as it does with any other hemoglobin-based blood (origin of blood cannot be identified).
3.3.2. Why
3.3.2.1. Oxidisation with haemoglobin and hydrogen peroxide causes the reagent to turn pink. The pink colour indicates the presence of haemoglobin which catalysted the breaking down of hydrogen peroxide to oxidising species.
3.3.3. Steps
3.3.3.1. STEP 1: Isolate the blood sample/s that glow/s in luminol test 2.
3.3.3.2. STEP 2: Add one drop of the blood sample on the filter paper provided.
3.3.3.3. STEP 3: Add two drops of the reagent to the blood sample.
3.3.3.4. STEP 4: Wait for three minutes and record observations.
3.3.3.5. STEP 5: Ensure no colours have developed yet and add two drops of hydrogen peroxide.
3.3.3.6. STEP 6: An intense pink colour should be observed for a positive test for peroxidise activity, and indicating haemoglobin (blood).
4. Chromatography Reg 4,9
4.1. definition:a physical separation method in which the components of a combination are separated by differences in their distribution.
4.2. variety of chromatographic processes:
4.2.1. Gas chromatography
4.2.1.1. Applications to real life
4.2.1.1.1. detect bombs in airports, identify and quantify such drugs as alcohol, used in forensics to compare fibres found on a victim
4.2.2. paper chromatography
4.2.2.1. comparison of rf values!
4.2.2.1.1. all substances have differing rf values
4.2.2.2. Applications to real life
4.2.2.2.1. separating amino acids and anions, RNA fingerprinting, separating and testing histamines, antibiotics
4.2.2.3. Steps taken
4.2.2.3.1. Step 1: Draw a line about 2cm from the bottom of the chromatography paper in pencil
4.2.2.3.2. Step 2: Add a drop of the required substance on=to the drawn line
4.2.2.3.3. Step 3: Lower the chromatography paper into the solvent, ensuring that the substance itself does not come into contact with the solvent
4.2.2.3.4. Step 4: Observe the different components of the substance distribute as the solvent moves up the chromatography paper
4.2.2.3.5. Step 5: Take out the chromatography and mark with a pencil, whee the solvent has reached.
4.2.2.3.6. Step 6: Measure the distance each component has travelled and the distance the solvent has travelled.
4.2.3. ion exchange chromatography
4.2.4. affinity chromatography
4.2.5. thin layer chromatography
4.2.5.1. Applications to real life
4.2.5.1.1. detecting pesticide or insecticide residues in food, also used in forensics to analyze the dye composition of fibers
4.2.6. liquid chromatography
4.2.6.1. Application to real life
4.2.6.1.1. test water samples to look for pollution
4.3. Possible reasons for chromatography
4.3.1. to determine whether the word is written with the same ink (tell whether words are forged
4.3.2. identify contaminants
4.3.3. identify different components of a substance
5. Blood Splatter 8, 22, 27, 29, 31
5.1. Amount of Blood
5.2. Physics of the blood splatter
5.2.1. Blood droplets are formed by the force of gravity (kniematics)
5.2.1.1. height of impact
5.2.1.1.1. New node
5.3. Properties of Blood
5.3.1. Shape of Blood
5.3.1.1. Blood forms a spherical shape due to surface tension of blood.
5.3.1.1.1. Surface Tension is contractive tendency of the surface of a liquid that allows it to resist an external force.
5.3.2. Viscosity
5.3.2.1. Viscosity is the measurement of the resistance of a fluid.
5.3.2.1.1. The viscosity of blood is higher than that of water.
5.3.2.1.2. Viscosity of blood: 3-4 mP·s-1
5.3.2.1.3. Viscosity of water: 1.0 mP·s-1
5.4. 4 phases of impact of blood
5.4.1. 1.contact/collapse
5.4.2. 2.Displacement
5.4.3. 3.Dispersion
5.4.4. 4.Retraction
5.4.4.1. New node
5.5. Factors that affect the blood splatter formed
5.5.1. angle and direction of impact
5.5.1.1. angle of impact is the acute angle that is formed between the direction of the blood drop and the surface it strikes
5.5.1.1.1. used to determine the area of convergence and the area of the origin
5.5.2. Velocity of impact
5.5.2.1. Different amount of force of impact will produce stain of different blood size.
5.5.2.1.1. From the size of the blood stain, we can predict the force of impact and the cause of injury eg. medium velocity impact caused by blunt force force trauma, high velocity impact splatter caused by gun shot wound
5.5.3. surface of the impact
5.5.3.1. the different types of the surface that the blood drops lands on, it would affect the size of the blood stain and the characteristics of the blood drop.
5.5.3.1.1. A blood drop that falls on a smooth surface has smooth edges while a blood drop that lands on a rough surface has ragged edges.
6. Fingerprinting 1,2,3,5,7,19,20
6.1. Fingerprinting Patterns
6.1.1. Arches (5% people)
6.1.1.1. Plain Arch
6.1.1.2. Tented Arch
6.1.2. Whorls (30-35% people)
6.1.2.1. Central Pocket Whorl
6.1.2.2. Accidental Whorl
6.1.2.3. Double Loop Whorl
6.1.2.4. Plain Whorl
6.1.3. Loops (60-65% people)
6.1.3.1. Ulnar Loop
6.1.3.2. Radial Loop
6.2. Identification Methods
6.2.1. Iodine Fuming method
6.2.1.1. For porous surfaces, e.g. paper
6.2.2. Superglue Fuming method
6.2.2.1. For non-porous surfaces, e.g. rubber, metal, electrical tape
6.2.3. Wood Glue Method
6.2.4. Powder Dusting Method
6.2.4.1. For hard, smooth, non-porous surfaces, e.g. tiles, mirrors
6.2.5. Via technology
6.2.5.1. Through AFIS which contains fingerprints of convicted criminals in case they commit crimes again after they are released thus as means of easy identification
6.3. Features of Fingerprints
6.3.1. Ridges
6.3.1.1. To grip and hold on to things via surface friction
6.3.2. Deltas
6.3.2.1. Connects two different types of lines on the pattern
6.4. Formed when substances like blood, dirt, ink and oils on the finger come into contact with a smooth surface.
6.4.1. A visible impression called fingerprints is left on the surface.
6.5. Types of Prints
6.5.1. Visible Prints
6.5.1.1. Visible to the naked eye and without development
6.5.2. Latent Prints
6.5.2.1. Not visible to naked eye. Formed through sweat. Must be developed.
6.5.3. Impressed Prints
6.5.3.1. Indentations on soft pliable surfaces. Can be viewable and photographed.