As forensic evidence

Scent as Forensic Evidence and Its Relationship to the Law Enforcement Canine, Charles Mesloh, http //www.uspcak9.com/training/forensicScent.pdf... 

Q (S3 Imagine that you are a lawyer. You are representing a client charged with possession of a controlled substance. The prosecutor introduces, as forensic evidence, the empirical formula of the substance that was found in your client s possession. How would you deal with this evidence as a lawyer for the defence ... 

Advantages Most forms of chemical analysis require vaporization, dissolution, or alteration of the analyzed sample in some way. Neutron activation analysis is a nondestructive process that can be used to study liquid, solid, or gaseous samples. Sensitive items, such as forensic evidence, meteorites, or artifacts, can be analyzed without harm. 

Perhaps the simplest examination done is the physical match. A small fragment of wood, plastic, or other material is recovered and fitted into a large piece found on the suspect or at the scene of the crime (39). Other examinations result ordy in demonstrating class characteristics (40). Such information may be used in a prosecution as circumstantial evidence in a trial. However, it is important that the forensic scientist neither inflate nor minimize (41,42) its importance. 

Informed debate and decisions on such important matters as the depletion of the ozone layer, acid rain and the quality of waterways all depend on the data provided by analytical chemists. Forensic evidence also often depends on chemical measurements. National and international trade are critically dependent on analytical results. Chemical composition is often the basis for the definition of the nature of goods and tariff classification. In all of these areas not only is it important to get the right answer but it is essential that the user of the results is confident and assured that the data are truly representative of the sample and that the results are defendable, traceable and mutually acceptable by all laboratories. 

But where did he come from Tie may have been raised in the same region where his body was found, or he might have been a newcomer to the area, or just traveling through. To determine which is the case, chemists and biologists have developed techniques that make use of certain isotopes. As with forensic evidence, these isotopes can be found in Otzi s teeth and bones. 

Hence, forensic research is exactly what revisionists, starting with Robert Faurisson, have called the search for material evidence. The revisionists demand for such material evidence is entirely consistent with the normal practice of modem law enforcement. Also, as is generally acknowledged, forensic evidence is more conclusive than eyewitness testimony or documentary evidence. 

We believe this book is timely, as soils are receiving increased attention as physical evidence. Thus far, the twenty-first century has seen an increase of peer-reviewed publications related to soils and forensic science of at least... 

Non-Polymeric Materials. Waxes, soaps, greases, asphalts, oils. Complex mixtures of hydrocarbons of different molecular weight when treated to a common thermal history (such as slow program-cooling from above the melt) give complex but highly repeatable characteristic DSC melting profiles (16,17). In the absence of any other forensic evidence, these thermal profiles should be sufficiently specific and repeat-able to be definitive evidence. 

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. 

The sequence of events associated with FDR examination is usually as follows the initial incident, apprehension of suspects, transporting of suspects to police station, sampling of suspects at police station (swabs of hands, face, head hair, and seizure of clothing), submission of items to the laboratory, sampling of clothing at the laboratory, sample preparation, analysis of samples, interpretation of results, preparation of statement of witness report, and the presentation of forensic evidence in court. 

In Chapter 22, Herr et al. describe a monoclonal antibody used to test for human albumin in body fluids. The development of this monoclonal antibody was aimed at forensic evidence, but if (and it must be tested) degradation processes do not destroy the antigenic site that this antibody recognizes, it could be used for archaeological samples. Certainly as these techniques are developed they will prove valuable in the studies of objects that are suspected of containing blood. For example, these newer methods could help further define an artifact like the Shroud of Turin, which is described in Chapter 23. 

The need for the identification of textile fibers in forensic science is a common one. Many types of crimes, when investigated, yield fibers as physical evidence. Crimes in which fibers may be deposited at the scene include robbery, breaking and entering, homicide, rape, assault, and hit-and-run accidents involving a victim. 

The value of the limit of detection In forensic work Is shrouded In details not usually present In other trace analysis efforts. In this area the performance of the analyst relates to samples submitted as legal evidence, perhaps for some crime. The sample may often be In such short supply that only limited analyses can be performed on It. In these cases the limit of detection can be greatly affected. 

The chemical characterization of forensic evidence from a crime scene or the criminal has some different requirements from that of many other types of chemical analysis. High sensitivity is important because the quantity of material for examination is often limited to minute traces found at the scene. The material under scrutiny must be characterized as comprehensively as possible to ensure maximum discrimination from other material in the same class. Forensic laboratories are multiinstrument facilities required to deal with many types of evidence found at a crime scene therefore, the routine methods used should preferably employ relatively inexpensive instrumentation. In order to protect integrity, samples should be analyzed as received if possible and any workup minimized. The method should preferably not be labor intensive. Pyrolysis-gas chromatography (Py-GC) and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) have proven to be an effective means of satisfying these requirements in many forensic science laboratories. - ... 

The sample techniques just described are designed for collection of transmission (absorption) spectra. This had been the most common type of IR spectroscopy, but it was limited in its applications. There are many types of samples that are not suited to the conventional sample cells and techniques just discussed. Thick, opaque solid samples, paints, coatings, fibers, polymers, aqueous solutions, samples that cannot be destroyed such as artwork or forensic evidence samples, and hot gases from smokestacks—these materials posed problems for the analytical chemist who wanted to obtain an IR absorption spectrum. The use of reflectance techniques provides a nondestructive method for obtaining IR spectral information from materials that are opaque, insoluble, or cannot be placed into conventional sample cells. In addition, IR emission from heated samples can be used to characterize certain types of samples and even measure remote sources such as smokestacks. In reflectance and emission, the FTIR spectrometer system is the same as that for transmission. For reflectance, the sampling accessories are different and in some specialized cases contain an integral detector. The heated sample itself provides the light for emission measurements therefore, there is no need for an IR source. There may be a heated sample holder for laboratory emission measurements. 

The importance of paints as physical evidence has been recognized for quite some time. In fact, paints are among those forensic materials that have engaged the attention of crime investigators and concerned scientists since the inception of forensic science laboratories, and they have always played important and crucial roles in crime investigation. 

Forensic Genetics. Forensic genetics is the use of human genetics in criminal or paternity cases. For example, DNA testing on blood, saliva, or other tissue can be used to determine the source of evidence, such as blood stains or semen, left at a crime scene. Forensic DNA analysis is also used to determine paternity and other kinship. Finally, with the increasing use of forensic genetics since the 1990 s, some incarcerated prisoners have been released after it was clearly determined that they could not possibly have been guilty of crimes they were convicted of, as DNA evidence eliminated them from suspicion. 

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