The Long Process of Forensic Investigation - Case Study Example

FZ3023- Drug Profiling Assignment In the given case, the first step in the long process of forensic investigation, the collection of evidence was already done. “The white powder, the mirror, the roll of cling film and clothing from all three suspects were removed and sent for forensic examination”. Initial examination on the clothing was also finished. The task now is to probe the identity of the white powder and prove that the white powder previously collected from the table and the traces of white powder from the sweatshirt tops of suspects A and B and from the fibers of the inside jacket pocket of suspect C are one and the same for them to be incriminated for drug trafficking. Forensic scientists employ several tests and techniques to provide evidence needed for the case. Analysis of samples is necessary to identify, quantify and drug profiling. The materials previously collected, 100 grams of white powder, the trace samples from the clothing of the suspects, the cling film and the mirror will all be subjected to analysis. Prior to the presumptive tests, physical description and sampling will be done. The physical characteristics such as texture, powder particle size, color, odor, taste and weight will be physically defined before a sample for analysis will be secured. It will be weighed and thoroughly homogenised, before a sample was taken. Presumptive analysis will provide the identification of the white powder collected from the table. Trace samples from the suspects’ clothing can directly be analyzed using confirmatory tests. Colour test will bring initial data for the powder’s identity. Specific color changes give the positive result for the powder’s identity. An intense blue-violet color when the powder is made to react with 1% cobalt acetate, and 5% isopropylamine in methanol of Dillie-Koppanyi test will identify it as a barbiturate. Marquis test using dilute solution of methanal in sulphuric acid can give two types of results; if the colour changed to purple, the powder is heroin-based, if the test however yields an orange-brown colour, the powder is an amphetamine. Treating it with a Duquenois-Levine test reagent and a purple colour resulted, the powder is positive as marijuana. In Scott test, in which a solution of cobalt chloride is added in a 50:50 mixture of water and glycerol, a blue colour positively identifies cocaine. This positive result can be confirmed by adding concentrated hydrochloric acid, liquid goes pink and then adding chloroform the blue reappears in the chloroform layer. Blue-purple in reaction with reagents of Van Urk test means the powder is LSD. Thin Layer Chromatography (TLC) is another presumptive analysis. Samples placed in plates can be analysed by UV light or a developing reagents i.e. iodine, potassium permanganate or sulphuric acid. TLC analysis results in a number of bands. Careful choice of developing reagent can allow selective tentative identification of a drug. Correct developing agent (Fast Blue BB salt) gives specific colours for specific cannabinoids: mauve for Cannabinol; orange for 9-THC; and light brown for Cannabidiol. Confirmation of the drug will follow after the initial data of drug’s identity was established. Such tests include microcrystalline and instrumental methods such as HPLC, GC, GC-MS. These are also methods by which the active component of the white powder will be extracted from the sample for confirmation of the substance’s identity. Microcrystalline tests will further give a specific profile for the powder. The tests identify one specific component and will also evaluate the relative concentration of a drug in the powder. The substance to be tested is mixed with a drop of a chemical reagent such as sodium acetate on a microscope slide and left until the chemical reaction produces crystals. The crystalline structure is viewed with a microscope under polarized light and is highly specific for a wide range of drugs. Needle-like crystals are characteristic of cocaine with platinic or gold chloride. Amphetamine with the reagent will produce rod-like crystals. Drugs are often mixed with other chemicals, called diluents, frequently sugars or starches. Simple solvent extraction and thin-layer chromatographic techniques can be used to separate drugs and diluents. Chromatography is a means of separating and tentatively identifying the components of a chemical mixture. It involves passing a mixture dissolved in a "mobile phase" through a stationary phase, which separates the analyte to be measured from other molecules in the mixture and allows it to be chemically isolated. The technique of thin-layer chromatography (TLC) incorporates a solid stationary phase and a mobile liquid phase to effect the separation of the constituents of a mixture. A thin-layer plate is prepared by coating a glass plate with a thin film of granular material, which is bonded to the plate with plaster of Paris. Solid samples must first be dissolved and a few microliters of the solution spotted with a capillary tube or syringe onto the granular surface near the lower edge of the plate. A liquid sample may be applied directly to the plate in a similar manner. The plate is then placed upright into a closed chamber that contains a selected liquid, with care that the liquid does not touch the sample spot. The liquid will slowly begin to rise up along the surface of the plate by capillary action. The rising liquid serves as the mobile carrier phase. As it moves past the sample spot, the components of the sample become distributed between the stationary solid phase and the mobile liquid phase. Those components with a greater solubility in the mobile liquid phase will travel up the surface of the plate at a faster speed. When the liquid front has moved a sufficient distance (usually 10 cm) the development is complete, and the plate is removed from the chamber and dried. Because most components are colorless (exceptions: organic pigments such as chlorophyll and beta-carotene) no separation will be noticeable after development unless the materials are visualized. To accomplish this, the plates are placed under UV light, revealing those materials that fluoresce as bright spots on a dark background. For identification purposes, a high confidence level necessitates the use of experimental standards which can be compared to the results for confirmation of the suspect material’s chemical composition.   Migration distances must therefore be matched with similar experiments on similar compounds using similar experimental configurations and apparatuses. If the distances are identical, then a tentative identification can be made. However, it must be cautioned that such identification cannot be considered definitive for the possibility always exists that numerous other substances can migrate the same distance up the plate when chromatographed under similar conditions. Thus, thin-layer chromatography cannot by itself provide an absolute and undisputed identification. Thus, TLC must be used in conjunction with other testing procedures in order to provide absolute proof of chemical identity.     Gas chromatography (or gas-liquid chromatography) separates mixtures on the basis of their distribution between a stationary liquid phase and a mobile gas phase. A chemically inert carrier gas (e.g. nitrogen or helium) flows through a column made of stainless steel or glass. The liquid sample under investigation is injected into a heated injection port by syringe, where it is immediately vaporized and swept into the column by the carrier gas. As the carrier gas flows through the column, it carries along with it the components of a mixture that have been injected into the column. Components will be separated according to their relative mobilities (and corresponding solubilities) in the mobile gas phase. As each component emerges from the column, it enters a detector. One type of detector uses a flame to ionize the emerging chemical substance, thus generating an electrical signal. The signal is recorded onto a strip-chart recorder as a function of time. This record is referred to as a chromatogram.  A typical gas chromatogram will show a series of peaks, each one corresponding to a specific component of the chemical mixture. The time required for a component to emerge form the column from the time of its injection is known as the retention time. This experimentally determined parameter serves as a useful identifying characteristic of a material (though it may vary for different instrument configurations). Gas chromatography has an added advantage in that it is extremely sensitive and can yield quantitative results. The amount of substance passing thru the GC detector is directly proportional to the area underneath the recorded peak. The amount of sample can often be determined to within the nearest billionth of a gram. Many of the uncertainties associated with vapor phase chromatography (GC) have been overcome by linking the gas chromatograph to a mass spectrometer to yield an extremely powerful combination known as gas chromatography / mass spectrometry (GC / MS). The separation of a mixture’s components is first accomplished on the gas chromatograph. A direct connection between the GC column and the mass spectrometer then allows each component to flow into the spectrometer as it emerges form the gas chromatograph. In the mass spectrometer, the material enters a high-vacuum chamber where a beam of high-energy electrons is aimed at the sample molecules. The electrons collide with the molecules, causing them to lose electrons and to acquire a positive charge. These positively charged (+) cations are highly unstable and rapidly decompose into smaller fragments. These fragments then pass through an electric or magnetic filed, where they are separated according to their masses. The advantage of this technique is that no two substances produce the same fragmentation pattern.    Hence, this fragmentation pattern serves as a “fingerprint” of a specific chemical substance. It is also sensitive to minute concentrations. With the data obtained from a GC/ MS determination, one can, with one instrument, separate the components of a complex drug mixture and then unequivocally identify each substance present in the mixture.  If the white powder is cocaine, its origin might as well be established to be considered and compared with the recently seized cocaine samples. The results of these analyses will be recorded and compared with the results of the tests with the cocaine samples which were seized at several other places. These indicators for comparison would include reduction in original compounds; presence of cutting agent Contac, adulterants and diluents; common adulterants such as procaine, benzocaine and ligndocaine; and common diluents such as lactose, mannitol, sucrose and dextrose. Cocaine samples could also be compared by their alkaloid content using three methods: Hydroxycocaine method, derivatisation with N,O-bis-trimethylsilyl acetomide, and Truxillic and truxinic acid method. All three types of profiling will be compared. To prove that samples are linked, all three different profiling techniques must show some relation. If the results were similar, the white powder is a part of the bulk of the cocaine circulating in the area. Tracing the origin of the powder has something to do with their packaging, content, and quality. The cocaine content and content of other alkaloids can be used to trace the origin of a cocaine sample: Ecuadorian cocaine levels are low; Columbian cocaine is characterised by high cinnamoylcocaine relative to cocaine; and Columbian cocaine has higher truxilline content than other varieties. How material is encountered can often indicate where it is from. Low quality cannabis in blocks were from West Africa and Caribbean; and either loose or wrapped would be from Central and Southern Africa. Higher quality cannabis tied around bamboo sticks are from South East Asia but if wrapped in paper, the cannabis came from Africa. Using HPLC, origin of opium and morphine could be determined. Turkish opium has codeine/morphine ratio of less than 0.1; Chinese opium has 3-4% high codeine; and Indian Opium has about 0.6 or less high noscapine/ morphine. Suspects A and B were caught red handed. When the profile of the white powder is finished and was proven to be a controlled drug and not a caster sugar as they claimed, they are directly implemented. Suspect C’s involvement is linked by the powder’s presence in his inside pocket and could further be implemented through fingerprinting of the cling film. The presence of the powder in his pocket suggests that he was directly involved in the delivery of the said powder and will be established by the fingerprints in the packaging of the powder. Reference Cole, Michael. ( ). Analysis of drug abuse. Forensic Science [PowerPoint Presentation] Retrieved: December 9, 2007 at www.hud.ac.uk/sas/forensic/evidence.ppt GB. (2007).Drug profiling [PowerPoint Presentation] GB. (2007).Drug profiling cannabis [PowerPoint Presentation] GB. (2007).Drug profiling cocaine [PowerPoint Presentation] GB. (2007).Drug profiling drug operations [PowerPoint presentation] GB. (2007).Drug profiling heroine [PowerPoint Presentation] GB. (2007).Drug profiling logos and packaging [PowerPoint Presentation] Huston, Robert. (n.d.) Forensic science center maximizes the tiniest clue. Forensic Sciences branch Allegheny County Medical Examiner’s Office. Saferstein, Richard. (2008). Forensic Science, An Introduction. Pearson Prentice Hall Read More