Forensic chemist

Physical evidence serves two purposes. In some cases it is used to prove a component or element of a crime. Eor example, in a case involving trafficking in cocaine [50-36-2] the prosecutor must prove that the white powder found in the criminal s possession was cocaine (Table 1). The forensic chemist tests the substance and issues a report. If the powder is methamphetamine [537-46-2] the charge must be amended. 

Gerichte. judicial, forensic, legal. amt, n. court, tribunal. -amtmann, m. judge, barkeit, /. jurisdiction, -chemie, /. forensic chemistry, -chemiker, m. forensic chemist legal chemist, -hof, m. court, tribunal, -rat, m. judge counselor. 

C03-0132. Police officers confiscate a packet of white powder that they believe contains heroin. Purification by a forensic chemist yields a 38.70-mg sample for combustion analysis. This sample gives 97.46 mg CO2 and 20.81 mg H2 O. A second sample is analyzed for its nitrogen content, which is 3.8%. Show by calculations whether these data are consistent with the formula for heroin, C21 H22 NO5. ... 

In the development of analytical methods one has to consider also cases where a fast response is required, e.g. clinical and forensic chemists or toxicologists need methods which yield results in a few minutes or hours to allow a fast response in cases of poisoning. In this event, accurate quantitative results may be of less importance, but the time from sampling to result may be lifesaving, whereas the throughput (i.e. number of analyses per day) is not so much of concern. 

Question 13.3 How Do Forensic Chemists Use Visible Stains to Trap Thieves 171... 

How do forensic chemists use visible stains to trap thieves See p. 170. 

The most important person in the DEA laboratory system is the forensic chemist. DEA requires the trainee chemist to undergo a special six-month training program. He is taught from the outset that each piece of evidence is unique and no step-by-step procedure can be written to cover all cases. 

In the past year, our forensic chemists participated with special agents in the seizure of over 30 domestic clandestine laboratories which were producing LSD, phencyclidine (PCP), dimethyl trypta-mine (DMT), methamphetamine, and liquid hashish. DEA chemists have also examined illegal laboratories in Europe, South America, and the Far East. These laboratories were producing heroin or cocaine. 

Parallels have been drawn between archaeological and forensic chemistry (Heron 1996), since the forensic chemist often has to deal with similarly small and degraded samples. In many ways, there is a close relationship between the two. Both derive evidence from samples obtained from a controlled recovery situation, and both attempt to reconstruct patterns of human... 

In 1979-1980, some illegal fentanyl analogues appeared that were being sold as substitutes for heroin on the street. Suddenly, a series of more than a dozen mysterious deaths occurred in southern California. Upon autopsy, the victims strongly looked as if they had overdosed on heroin however, no traces of heroin could be found in their bodies. Later, forensic chemists identified a fentanyl analogue (alpha-methyl-fentanyl) that was present in all of the victims. As it turns out, alpha-methyl-fentanyl was being sold on the streets under the name China White (Figure 7.2), because it resembled (and contained) pure synthetic heroin that was produced in Southeast Asia. 

The novel horizons in natural product chemistry are a consequence of advances in mass spectrometry instrumentation. Current applications comprise the elucidation of natural products as part of total extract mixtures in samples of interest to environmental chemists, archaelogists, paleobotanists, geologists, oceanographers, atmospheric chemists, forensic chemists and engineers. The list of applications is expected to expand and some examples are discussed in this chapter. 

Crippin first started his career in forensics in 1977 and still is extremely active in the field of forensic science. From August 1978 to August 1984, he served as forensic chemist with the Missouri State Highway Patrol system. In August 1984 he was promoted to laboratory supervisor of the St. Joseph, Missouri, Troop H laboratory. During his tenure with the Missouri State Highway Patrol, he was responsible for working all of the explosive incidents in the state. 

Forensic Chemistry (Chemical Criminalistics). This branch of science relates to the application of chemical knowledge and techniques to die study of physical evidence connected with crime. Investigation of firearms, ammunition and expls is one of the duties of a forensic chemist Refs i) A. Lucas, "Forensic Chemistry and Scientific Criminal Investigation 1, Longmans, Green, London (1935), Chap 7, Explosives Chap 11, Fireworks 2) H. 

Either through instrumental analysis or qualitative analysis, the forensic chemist can reveal the presence of ions in a paint chip from an artwork and use the ion information to detect an art forgery. 

But there are signs that simpler, less expensive LC/MS systems designed and priced for the general laboratory bench chemist, production facilities, and quality control laboratories may soon be possible. It remains to seen whether manufacturers will decide to produce these systems. Older MS systems have been purchased, attached to HPLC systems equipped with relatively inexpensive interfaces, and pressed into service for molecular weight determination as a 30,000 detector, indicating that the desire and need exists for general laboratory LC/MS systems. As prices continue to drop and technology advances work their way out of the research laboratories, the LC/MS will become a major tool for the forensic chemist whose separations must stand up in court, for the clinical chemist whose separations impact life and death, and for the food and environmental chemist whose efforts affect the food we eat, the water we drink, and the air we breathe. 

Numerous methods are available in the recovery of trace quantities of flammable accelerants from arson debris. Of these, four basic methods are generally preferred and have been found to be adequate in most cases encountered by forensic chemists. Each of these methods possesses good and bad features and consideration must be given to those features in contemplating the recovery of accelerants from any particular piece of evidence. 

However, this procedure is limited in recovering accelerants from mixtures of foaming agents such as soaps. These items are frequently encountered by the forensic chemist in sabotage cases and incendiary devices. 

In addition, the mixing of two or more accelerants may produce a sample that is virtually impossible to identify. The chromatogram produced from such a sample is difficult to associate with a single original accelerant or with a known mixture of accelerants prepared by the forensic chemist since he is estimating the ratios of accelerant mixtures he suspects to be present in the questioned sample. 

Futhermore, difficulty is encountered with many specimens received for examination either because of the absence of accelerant or because of the type of material itself. Examples are (a) heavily charred wood, where all flammable accelerant has been lost, (b) a rag that was soaked in the water used by the fire department to extinguish the blaze, dried out, and forwarded to the forensic chemist for examination and (c) a sample of soap recovered near the site or origin. Analysis of the soap for an accelerant would exclude the solvent wash recovery method as well as any other method that might cause interference due to foaming. 

If a sample is prepared correctly, no vapors of accelerants will be lost once it is placed in an adequate container and properly sealed ( 3). Many good specimens are handled subsequent to recovery in such a way that the flammable accelerants present are lost. Upon reaching the forensic chemist, he either has very little accelerant to recover and examine, or he has none. Porous containers and wrappers such as paper bags, bundles of newspapers and cardboard boxes are frequently substituted for suitable airtight containers. In these instances, volatile materials are invariably lost through evaporation. 

Through the use of the various methods of recovery discussed, it is often possible for the forensic chemist to obtain a satisfactory sample of accelerant residue for examination purposes. Through utilization of gas chromatography, the identification of the accelerant can often be effected and differences and similarities between recovered and known standard specimens can be shown. However, success in the recovery and identification of accelerant residues is highly dependent upon the type and quantity of material received for examination and the care that has been taken in the preservation of the items to be examined. 

Obvious areas of potential research present themselves to the forensic chemist. 

Physical evidence collected at crime scenes is sealed in special containers to prevent contamination and degradation and is catalogued carefully. A chain of custody is established and documented as the evidence is sent to a forensic laboratory. At the laboratory, the evidence is examined by personnel trained in one of several fields Forensic serologists examine body fluids, forensic pathologists examine human remains, firearms technicians classify and test firearms and explosives, and forensic chemists determine the composition and identity of materials. 

Every chemist is schooled in general, organic, and analytical chemistry, but forensic chemists also specialize in specific areas of expertise. For example, an inorganic chemist may examine traces of dust by using micro-chemistry to identify the chemical composition of tiny particles. Another chemist might employ thin-layer chromatography during the analysis of... 

The fact that most samples examined are not pure substances, but are often mixed with dirt or debris, presents a major challenge to the forensic chemist. This may also be an advantage, as every substance collected at a crime scene is a unique mixture of chemical compounds that can ultimately be identified. Arsonists, for example, often use accelerants such as gasoline or kerosene to speed combustion and spread flames in the interior of a building. A forensic chemist may collect samples of burned and unburned materials, extract the volatile hydrocarbons, and separate the components for analysis by gas chromatography. 

The identification of drugs of abuse represents the most prominent use of chemistry in forensics (Berry 1985 Hasan et al. 2008). Activities were developed that focused on the techniques used by forensic chemists to identify illicit drugs, including both presumptive and confirmative tests. These activities were applied to laboratory chemicals that could be purchased without a drug license. The first activity involved... 

Providing crucial, hard-to-find data for forensic laboratories and forensic chemists with little or no prior knowledge of firearms, this seminal work presents a wide range of firearms chemistry information and outlines the creation of an international statistical database to aid investigations. 

Cocaine is a white solid which melts at 98°C when pure. A forensic chemist working for the New York City Police Department has a white solid believed to be cocaine. What can the chemist do to quickly determine whether the sample is cocaine and whether it is pure or a mixture ... 

Did the eccentricities of the great artists stem from their being victims of low-level poisoning Lead and mercury are well known to affect the brain. Given the skills of today s forensic chemists it might one day be possible to reveal more about the great painters themselves provided we can find at least a strand of their hair or some part of their remains. 

All chemists who try to identify unknown compounds are like detectives. Forensic chemists, however, actually work with investigators. They use their chemical knowledge to help explain evidence. Forensic chemists are especially helpful in an arson investigation. 

What other types of crime could be solved by a forensic chemist Brainstorm a list. 

What other instruments might a forensic chemist use to identify compounds Using the Internet or reference books, do some research to find out. 

A forensic chemist analyzes some white pills found in an aspirin bottle on an unidentified dead body. One pill is found to consist of 60.05% potassium, 18.44% carbon, and 21.51% nitrogen. A second pill contains 60.00% carbon, 4.48% hydrogen, and 35.53% oxygen and has a molar mass of 180 g/mol. Can these data help the forensic chemist deduce whether the death was accidental, murder, or suicide ... 

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