Short Answer: 1. Briefly describe the basic chromatographic process. Be sure to detail the role of the stationary and mobile phases.

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1 Murphy Brasuel: Intro to Forensic Science Quiz 2 Blk 2, Honor Code: Group. You may NOT talk to people or to other living, non-spiritual beings outside the group. Except for the last question which requires you to visit the lab the quiz may only be completed in the classroom, Olin lounge (if available) or the classroom next door if open. Short Answer: 1. Briefly describe the basic chromatographic process. Be sure to detail the role of the stationary and mobile phases. The chromatographic process depends on the distribution of the compounds you wish to separate between two phases. Depending on the intermolecular forces in the compound it will prefer to distribute mainly to one or the other of the phases. If one of the phases does not move (stationary phase) and one phase is moving (mobile phase) the substance will move slowly if it prefers the stationary phase and will move quickly if it prefers the mobile phase. Most compounds will have a different strength of preference for either the mobile or stationary phase and thus will separate. Chromatography allows us to separate the components of a complex sample. 2. (a) (Essay) Explain the characteristics of glass fractures and the types of cracking that form from application of weight (strain) to the glass. Explain as completely as possible, use back of page if necessary. Glass may be subjected to three types of forces (strains): compressive force, which squeezes the material; tensile force, which expands the material; and shear force, which slides one part of the material in one direction and another part in a different direction. Each of these forces causes a deformation, which is resisted by the internal cohesion (stress) of the material. Glass breaks when a tensile strain is applied that is sufficient to overcome the natural tensile stress limit of the material. When compressive strains are placed on glass that cause a tensile strain, cracks will appear and travel in two directions. First, they will grow from the unloaded side to the loaded side. Second, they will radiate outward, away from the load point; they are therefore called radial cracks. If the load persists, new cracks will form, called tangential cracks or concentric cracks, and the resulting pattern has a spider web appearance. Note that radial cracks grow from the load point outward and from the unloaded side to the loaded side. In contrast, tangential cracks grow from one radial crack to another and from the loaded side to the unloaded side. When a bullet is shot at the pane of glass, the load is a projectile. The load side is known as the entrance side, and the unloaded side is called the exit side. As the initial velocity of the projectile increases, the central hole becomes smaller, the cracking patterns become simpler, and the central hole develops a pattern wherein the exit hole is invariably wider than the entrance hole. Examination of the edges of broken pieces of glass will reveal a set of curved lines known as rib marks (or stress marks). In a radial crack, the rib marks will be nearly perpendicular to the unloaded (or exit) side and nearly parallel to the loaded (or entrance) side. Things will be exactly reversed for a tangential crack. The 3R rule helps in remembering this pattern: Radial cracks give rib marks, which make Right angles on the Reverse side form where the force was applied. The direction of lateral propagation of the crack is always from the concave sides of the rib marks toward their convex sides

2 (b) There is a broken piece of glass in the lab. Was the force that caused the breakage applied to the frosted side or the unfrosted side? Explain how you know. Upon reconstruction of the glass plate it is immediately evident that only radial cracks exist. The stress mark seen in these radial cracks are parallel to the unfrosted side and perpendicular to the frosted side. From the 3R rule this indicates that force was applied from the unfrosted side of the glass. 3. Explain the refractive index and common testing methods used in analysis of glass. Light has wave properties. As a result, a beam of light traveling from a gas into a solid undergoes a decrease in its velocity, such that the beam bends downward as it passes from the air into the glass. The bending of a light beam as it passes from one medium to another is known as refraction. The refractive index, which is a measure of how much the light is bent as it enters the glass, is the ratio of the velocity of light in the air to the velocity of light in the glass being measured. When using the oil immersion method to measure the refractive index, the forensic examiner places the questioned glass fragments in specialized silicone oils, whose refractive indices have been well studied. The refractive index of virtually all window glass and most bottles can be compared by using silicone oil as the comparison liquid and by varying its temperature between 35 C and 100 C. An easy way to vary the refractive index of the immersion oil is to heat it. As the temperature increases, the refractive index of the oil decreases until the Becke line and the glass fragments disappear. At this point (called the match point), the refractive indices of the oil and the glass fragment are the same. The Emmons procedure, which was developed by the Association of Official Analytical Chemists, uses a hot stage microscope in conjunction with different source lamps. It measures the index of refraction at a variety of wavelengths. We can also use mixtures of clove and olive oil to match the index of refraction of a piece of glass. We then would measure the refractive index of this mixture. 4. Explain how documents can be traced to a particular typewriter. Because it takes physical force to strike the ribbon onto the paper, as manual typewriters are used, their typing mechanism becomes increasingly more worn. This wear, which occurs in a random and irregular way that depends on the habits of the user, imparts to the typewriter individual characteristics. Variations in alignment, both vertical and horizontal, and misalignment of individual letters are also often used to identify an individual typewriter as having produced a certain document. Familiarity with the specific typefaces used by typewriter manufacturers often aids the document examiner in identifying the model and manufacturer of the typewriter used to produce a certain document.

3 5. What steps should investigators take to prevent suspects from staging their writing specimens? When obtaining a writing specimen, the investigator should furnish the suspect with a pen and paper that are similar to those used to create the questioned document. The investigator should not show the suspect the questioned document or provide the suspect with any help with spelling, punctuation, capitalization, or grammar. He or she should dictate text that contains as many of the same words and phrases that appear in the questioned document as possible, and should dictate this text three times. If the suspect is trying to deliberately alter his or her writing, wide variations will be observed between each specimen. 6. Describe two commonly used methods of serial number restoration in firearms The magnaflux method is designed to restore serial numbers that are imprinted on iron or steel. This method begins by using pretreatment with a small grinding tool to smooth the obliterated surface. A magnet is then attached to the opposite side of the firearm, directly behind the obliterated area. Next, a mixture of fine iron filings and light oil is applied to the obliterated area. The metal filings arrange themselves in the oil to provide a shadow of each number, allowing visualization of the serial number. The major advantage of this technique is that it is nondestructive. In the acid etching method, the obliterated area is pretreated with a small grinding tool to smooth down the obliterated area. Acid can then be used to etch the surface. Because of changes in crystal structure the location of the original numbers will etch at a different rate then the surrounding metal. I don t expect you know reagent mixtures but some common ones are: Fry s reagent a mixture of hydrochloric acid, copper chloride, ethyl alcohol, and water is then carefully applied to the area of interest. It then slowly dissolves away the extraneous scratches and markings, revealing some of the numbers imprinted in the metal. Vinella s reagent is used to restore serial numbers on aluminum alloys; it is a mixture of glycerol, hydrofluoric acid, and nitric acid. Hume-Rothery solution is a mixture of copper chloride, hydrochloric acid, and water. Often forensic examiners alternate successive treatments of Vinella s reagent followed by treatment with Hume-Rothery solution. Because many applications of these chemicals are necessary, the acid etching method is painstakingly slow. Once the number is visible, the acid may continue to react with the metal, which will eventually destroy the number. For this reason, extreme care should be taken to record the procedures and their results (photographically) because etching cannot be repeated a second time. 7. Explain inductively coupled plasma optical emission spectroscopy. Inductively coupled plasma optical emission spectroscopy (ICP-OES) is a technique that uses an argon ion plasma. The argon ions are accelerated by the oscillating radiofrequency and form a closed annular torch that reaches temperatures as high as 10,000 C and has the shape of a doughnut. The most commonly used device for sample injection is a nebulizer. Once injected, samples are carried into the torch by argon flowing through the central quartz tube. In the torch, the solvent is stripped from the metal ions, electrons are captured by the ions, and the extreme heat of the torch thermally excites the metal atom into an excited state. As the excited metal atom leaves the torch, it cools down and relaxes to the ground state. In so doing, the atom releases a photon of light a process called optical emission. The forensic scientist can determine which elements are present by measuring the different wavelengths given off.

4 8. Compare and contrast the GSR tests of atomic absorption spectroscopy and scanning electron microscopy analysis. In atomic absorption spectroscopy (AAS) analysis, GSR is collected for the analysis by using a special kit that contains vials, cotton-tipped swabs, and dilute nitric acid. The kit containing the swabs is sent to the crime lab, where an analyst removes each swab from its vial and carefully treats it with a dilute nitric acid solution to remove the dissolved GSR. To determine the elements present in the sample, the forensic examiner uses an atomic absorption spectrometer with a flameless graphite furnace atomizer. In this way, he or she can determine the concentrations of lead, antimony, and barium released from the primer when the gun was fired and to determine whether gunshot residue is, in fact, present. The AAS measures one element at a time which is the major disadvantage of this GSR detection technique. Scanning electron microscopy (SEM) can reveal the finest details of structure of the GSR. In SEM analysis, the investigator applies an adhesive tape directly to the suspect s hands (or other surface) to lift the GSR. In the cap of each tube of the GSR sampling kits is an aluminum stub consisting of an electrically conductive adhesive layer protected with a cover. The investigator dabs the stub over the suspect s hand; the gummed surface of the adhesive removes the GSR from the skin. An alternative collection method uses polyvinyl alcohol (PVA) as the basis for removing the GSR; this technique is useful if the skin is partially covered in blood. Electrons, which are produced in the electron source, travel through a specimen in a way that is similar to a beam of light passing through a sample in a light microscope. Some of the electrons that strike the surface of the GSR sample are immediately reflected back toward the electron source; these are called backscattered electrons. By measuring the energy of the emitted X-rays, the elemental composition of the surface can be determined by a technique called energy-dispersive X-ray spectroscopy (EDX). From SEM-EDX the examiner can obtain both the morphology and chemical composition of the GSR particles. This can be important in distinguishing environmental or planted false positives for GSR. 9. Describe what burn patterns can tell you about the origin and cause of a fire. Fire patterns are the physical marks and char that remain after a fire. Lines or darkened areas are often found on surfaces after a fire, and they record the boundaries between different levels of heat and smoke produced at the fire scene. Markings left on surfaces depend on the composition of the material. Damage to surfaces will be more severe on the side of that surface from which the fire was set. The direction in which the fire traveled can be determined by examining any burn holes in walls or ceilings. Generally, the fire will have originated from the wider side of the burn hole. The remains of damaged material at the fire scene may also provide clues about the source of the fire. Wood, for example, undergoes a chemical decomposition when it is exposed to elevated temperatures. Most of the remaining solid residue after wood burns is carbon, often referred to as char. By measuring the depth and extent of charring, the investigator may be able to determine which part of a wooden structure was exposed longest to a heat source information that can be used to estimate the duration of the fire.

5 10. Using the sheet of racial characteristics provided upstairs identify the predominant racial characteristics of the skull you will find in the lab. Carefully explain your answer. Only one group at a time!! Evidence from profile observation: This is a very flat face. Could indicate caucasian or mongoloid. Cheekbones are projecting forward in comparison to the nasal cavity. Thus this skull is mongoloid (or American Indian). Evidence from quantitative skull measurements: Naso-maxillo frontal subtense 1.10 Maxillofrontal indice 41.0% maxillo frontal breadth 2.64 Naso-zygoorbital subtense 1.80 Zygoorbital indice 31.5% zygoorbital breadth 5.70 naso-alpha subtense 1.02 Alpha Index 55.4% alpha cord 1.84 Between the observations and the measurements this skull in mongoloid (and Male).