Forensic methods microscopy

The identification and comparison of wood are an area of forensic interest. Microscopy methods on the basis of morphology are generally used for this purpose. However, developments in the nud-1990s indicate that there is potential for the chemical taxonomy of wood spedes by THM and also by the pyrolysis of TMAH extractives. ... 

FTIR microspectroscopy (or FTIR microscopy or /r-FTIR) has been a conventional method for materials characterization since 1984, when Analect Instruments (now KVB) introduced a transmission microscope interfaced to its AQS FTIR [181]. Since then, FTIR microspectroscopy has developed into a greatly advanced tool for the analysis of thin films on a wide variety of snbstrates (including a single particle, cell, bacterium, or fiber) for scientific, industrial, and forensic applications [182-I9I]. Examples include oxide layers on technical Si wafers [192], organic films on Si (001) [193], organic [194-196]... 

An application of ATR IR microscopy in forensic science is provided in Fig. 4.38. It involves detecting cosmetic treatments found on hair fiber surfaces [237]. If this sample were to be analyzed by the transmission method, the spectrum would show predominantly protein from the bulk fiber. However, by jx-FTIR ATR spectroscopy, the contribution of the hair coating can be distinguished. For this example, a hair fiber was mounted on a glass slide and held in place at both ends with double-sided sticky tape. By placing the sample on a glass slide, the illumination from below the sample can be used to aid in viewing the sample with the survey mode of the ATR objective. A ZnSe IRE (n = 2.4)... 

Creatinine. Electrophoresis Principles Isoelectric Focusing. Enzymes Enzymes In Physiological Samples Industrial Products and Processes Enzyme Assays. Forensic Sciences Alcohol In Body Fluids DNA Profiling Systematic Drug Identification Thin-Layer Chromatography. Immunoassays Applications Forensic. Microscopy Applications Forensic. Nucleic Acids Electrochemical Methods. Polymerase Chain Reaction. Spectrophotometry Oven/lew Biochemical Applications. 

Chemical features determined by analysis of elements in human hair are helpful for hair comparisons. Analysis of elements in the hair has been accomplished by instrumental methods such as atomic absorption spectrometry, neutron activation analysis, energy dispersive X-ray microanalysis (EDX). Among them, EDX equipped with scanning electron microscopy is widely used in forensic hair examination because it facilitates easy analysis of elements whilst observing the hair structure. 

During an examination under the stereomicroscope, particles of particular interest are isolated and mounted for examination by polarized light microscopy, typically the next step in a forensic microscopical examination. By this point, the microscopist typically has a good idea of the material being observed, or at least the class of material, which aids in the choice of method for mounting the particle for additional analyses. 

This case example serves to illustrate several points first, that forensic microscopy should be applied as an early line of examination rather than a late one. The above case is a prime example of an examination in which an investigative, rather than comparative, approach may have likely led to an earlier resolution of a serial murder case. Second, the scientific approach pursued in each case involving the microscopic examination of trace evidence may be different. Thus, the forensic microscopist must be a true scientist who is able to adapt the techniques and methods available to the requirements of the case at hand and not be bound to a standardized procedure devised for the use of technicians. 

See also Blood and Plasma. Clinical Analysis Glucose. DNA Sequencing. Fluorescence Overview. Forensic Sciences Drug Screening in Sport. Microscopy Techniques Electron Microscopy Scanning Electron Microscopy Atomic Force and Scanning Tunneling Microscopy. Nucleic Acids Spectroscopic Methods. Raman Spectroscopy Instrumentation. Sensors Overview. 

Abstract A short history and treatment of the various aspects of nuclear forensic analysis is followed by a discussion of the most common chemical procedures, including applications of tracers, radioisotopic generators, and sample chronometry. Analytic methodology discussed includes sample preparation, radiation detection, various forms of microscopy, and mass-spectrometric techniques. The chapter concludes with methods for the production and treatment of special nuclear materials and with a description of several actual case studies conducted at Livermore. 

The nature of the specimen and the question that has been raised about it determine the course of action and the avenue of the analysis. After consideration of all known facts, and after nondestructive observations are completed, a particular test is selected in an attempt to answer a specific question. The results of this test determine the next step chosen. Some of the methods that may be employed for specific groups of polymers are discussed in the following sections. Microscopic and spectroscopic methods yield a great amount of information in the least amoimt of time, and, subsequently, are most frequently used by forensic trace examiners. Therefore, microscopy and spectroscopy are discussed in the greatest depth. 

In this chapter, we delve into the instrumental tools, techniques, and procedures utilized in forensic chemistry. The chapter is best thought of as akin to a ClijfsNotes of that enormous topic, a supplement to and summary of the many fine works listed in the "References" and "Further Reading" sections at the end of the chapter. For those who have recently taken an instrumental analysis course, much will be review for those who have not, enough information is provided to imderstand how and why the instruments are used and to understand information presented in the chapters that follow. Mass spectrometry and infrared spectrometry often are covered in an organic chemistry course, at least to the level of detail assumed here. The depth and breadth of each treatment corresponds to how widespread its application is in forensic chemistry. For example, inductively coupled plasma mass spectrometry (ICP-MS) was introduced in the mid 198(te and is routinely used in many materials, environmental, and research laboratories. However, it is rarely applied to forensic chemistry and hence is omitted here. Conversely, microscopy is a staple of forensic science and is not frequently used in other analytical settings. The presentation of each method is necessarily concise and is meant to provide information requisite to an understanding of later topics it is not meant as a replacement for an instrumental anal)reis course. 

Kohler developed the illumination pathway that is standard today in forensic microscopy. He worked extensively in the field of photomicrography, an infant science in the late 1800s. Kohler used the method of illumination now named after him to obtain full, even, and bright lighting of specimens that was essential for early photography. 

XRF is readily adaptable to microscopic platforms and is used for surface mapping applications. Forensically, the most important micro-XRF method is that associated with scanning electron microscopy (SEM), which uses electron beams as opposed to photon beams to visualize a sample. Consequently, X-ray emission is a natural and exploitable byproduct of this interaction. The prevalent adaptation for forensic work is the SEM-EDS configuration illustrated in Figure 5.49. Electrons are emitted from a filament or other source and are focused onto the sample, whereupon the beam scans the surface. There are instruments that target transmitted electrons (transmission electron microscopy, or TEM), but they are not widely used forensically. 

In many studies, particularly those related to materials and forensic science, it is frequently necessary to measure a mid-infrared spectrum from a trace amount of a sample or a sample of small size. In some circumstances, this may be accomplished by using a beam-condenser accessory within the conventional sample compartment of a Fourier-transform infrared (FT-IR) spectrometer. Perhaps today though, it is more convenient to use infrared microspectrometry (often commonly referred to as infrared microspectroscopy or even infrared microscopy). Based on an optical microscope (or infrared microscope) coupled to an FT-IR spectrometer, it is one of the most useful methods for structural analysis of such samples and can often be undertaken in a non-destructive manner [1, 2]. 

In almost all cases, the forensic hair examiner is seeking to determine whether certain hairs found at the scene of a crime or on the person of someone involved in a crime could have come from a particular person. Although recent research indicates that pyrolysis-gas liquid chromatography (Munson and Vick, 1985) or electrophoresis (Lee et al., 1978 Budowle and Acton, 1981 Marshall and Gillespie, 1982 Marshall, 1984) may have some value in the comparison of hair samples, the method routinely used in forensic science laboratories for hair comparisons is comparison microscopy (Bisbing, 1982). The questioned hairs are compared with hairs of known provenance, using features such as diameter, diameter variation, color,... 

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