Forensic+Science+Key+Points


 * Forensic Science Key Points** - these are the things you //need// to know from each lesson...

//Lesson 1: Introduction// - Scene of Crime Officers (SOCO's) must protect a crime scene and avoid contaminating evidence by:
 * 1) Restricting access with tape to mark out the boundary of the crime scene;
 * 2) Wearing protective clothing such as paper suits, masks, over-shoes and gloves;
 * 3) Using suitable methods of collecting and storing samples, and recording infromation, such as labelling evidence bags and taking photographs.

//Lesson 2: Fingerprints//
 * 1) There are three main types of fingerprint: Loops, Arches and Whorls (remember - L.A.W.)
 * 2) The common ways of recovering fingerprints are:
 * Powder dusting;
 * Quaser illumination (ultraviolet light causes oils in the ridges to fluoresce);
 * Superglue fuming (Superglue is vaporised and bonds with the oils in the ridges).

//Lesson 3: Glass - The Invisible Evidence//
 * 1) Light refracts (bends) towards normal when it enters glass.
 * 2) We can find the Refractive Index by measuring the angle of incidence and the angle of refraction.
 * 3) Oil immersion method: a glass fragment disappears when put into oil with the same refractive index.

//Lesson 4: Microscopic evidence//
 * 1) Forensic Scientists use comparison, polarising and electron microscopes to improve contrast and resolution. This provides more accurate and reliable evidence than simple light microscopes.
 * 2) The pores and furrows of pollen grains and the layers of paint have distinctive features.
 * 3) Trace evidence can link a suspect to a crime scene.

//Lesson 5: Impressions//
 * 1) Footprints, tyre tracks and tool marks are examples of impressions.
 * 2) To record an impression at the crime scene, a SOCO can make plaster casts and take photographs.
 * 3) When recovering footwear from a suspect, an impression can be made by inking and taking a photograph.

//Lesson 6: Distinguishing different substances//
 * 1) The properties of substances can be used to identify the substances.
 * 2) Ionic compounds have high melting points, while most covalent compounds have low melting points and melting points.
 * 3) Ionic compounds have ionic bonds netween positive metal ions and negative non-metal ions, such as in sodium chloride, NaCl. To break the bonds needs alot of energy.
 * 4) Organic compounds have covalent bonds, like Glucose. To seperate, molecules only need a little energy.

//Lesson 7: Testing for ions//
 * 1) You use a precipitation reaction to identify ions in solution.
 * 2) A precipitate is an insoluble solid. It's colour can be used to help identify the substance.
 * 3) The sodium hydroxide (NaOH) test uses this idea to identify metal ions.

//Lesson 8: Flame tests//

You can use a flame test to identify metal ions in a solid.
 * **Metal Ion** || **Flame Colour** ||
 * Sodium || Bright Yellow ||
 * Potassium || Lilac ||
 * Copper || Green-Blue ||
 * Calcium || Brick Red ||

//Lesson 9: Chromatography//
 * 1) You use chromatography to separate and compare mixtures like inks.
 * 2) Different substances travel different distances, depending on how each clings to the stationary substance.
 * 3) In Paper Chromatography, the stationary substance is the paper containing trapped water molecules. Paper contains about 10% water. In Thin Layer Chromatography (TLC) the stationary substance is a layer of powder coated onto a sheet.

//Lesson 10: Blood and DNA//
 * 1) Blood contains red blood cells, white blood cells, platelets and plasma. The four main blood groups are A, B, AB and O.
 * 2) Electrophoresis is like electrically forced chromatography. It separates the DNA fragments to produce a DNA profile. Everyone's DNA profile (like a fingerprint) is unique.

//Lesson 11: Databases//
 * 1) A database match can link a suspect to a crime. A mismatch can exclude a suspect from an investigation. Examples include NAFIS (National Automated Fingerprint Identification System) and NDNAD (National DNA Database).
 * 2) The description of a criminal by a witness may be recorded using 'identikit' or an 'artists impression'.

//Lesson 12: Presenting Evidence//
 * 1) A forensic scientist's report presents evidence and conclusions for a court.
 * 2) Conclusions, based on the evidence, state whether or not a suspect was at the crime scene or commited the crime.