Crime materials

One essential factor that differentiates this type of analyses from other analytical procedures is that the trace is the result of a past and uncertain action and its quantity cannot be modified. One can only assume that it is representative of the chemical makeup of the source and this assumption has to be taken into account when interpreting results. An essential limiting factor therefore comes from the sample that cannot be selected as in a true sampling procedure except when mass produced crime material is seized (illicit drugs, counterfeit). 

Trace Evidence. Trace evidence (23) refers to minute, sometimes microscopic material found during the examination of a crime scene or a victim s or suspect s clothing (see Trace AND residue analysis). Trace evidence often helps poHce investigators (24) develop connections between suspect and victim and the crime scene. The theory behind trace evidence was first articulated by a French forensic scientist the Locard Exchange Principle notes that it is not possible to enter a location, such as a room, without changing the environment. An individual brings trace materials into the area and takes trace materials away. The challenge to the forensic scientist is to locate, collect, preserve, and characterize the trace evidence. 

Searching a crime scene is a complex process (25), involving poHce, crime scene technicians, and forensic scientists. The procedure requires careful documentation, collection, and preservation of the evidence. Trace evidence (26) in criminal investigations typically consists of hairs (27,28) both natural and synthetic fibers (qv) (29,30), fabrics glass (qv) (31,32) plastics (33) sod plant material budding material such as cement (qv), paint (qv), stucco, wood (qv), etc (34), flammable fluid residues (35,36), eg, in arson investigations explosive residues, eg, from bombings (37,38) (see Explosives and propellents), and so on. 

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. 

Forensic Serology. Blood, often associated with crimes of violence, is powerfiil physical evidence. Its presence suggests association with the criminal act and blood can be used to associate suspects and locations with the bleeder. Blood is a complex mixture of cellular material, proteins, and enzymes and several tests are available for suspected bloody evidence. A typical test protocol involves (/) determining whether blood is present, (2) determining if it is human blood, (J) typing the blood, and (4) when appHcable, performing DNA typing. 

Emergency responses to incidents involving weapons of mass destruction are much different from responses to incidents involving conventional explosives. For example, while the debris from conventional explosives may be extensive and present hazards to the individuals responding, such as fires or structural instability, the materials are not inherently hazardous. In this situation, the site can be secured and forensic investigations can be conducted similarly to investigations at other crime scenes. 

Apart from the use of practical explosive tests to assess damage patterns at a crime scene, it has been suggested that patterns of deposition of explosives residue could be similarly assessed [27]. Practical experience shows that even in a planned scientific experiment there are huge variations in residue deposition patterns because of the difficulty of controlling aU the relevant parameters. Events at a crime scene are completely uncontrolled and subject to even greater variations, and to make matters worse the design, placement and performance of the explosive device are at best inferred rather than known. The presence of chemical traces of a particular explosive at a bomb scene is a useful indication of the material used the drawing of any conclusions beyond that point should be subject to extremely cautious consideration. 

Under federal law, silencers are treated in the same category as automatic weapons. Armor-piercing ammunition (popularly called cop-killer bullets) were banned in 1986, with an expanded definition of banned bullets in the Violent Crime Control and Law Enforcement Act of 1994 that includes bullets made of tungsten, beryllium, depleted uranium, and other exotic materials. Other accessories can also cause a weapon to be banned (see Assault Weapons above). 

Forensic Science, it is discussed under the title "Forensic Emphasis Shifts to Broader Role" in C EN, Feb 5, 1973, pp 13-15 s stated that crime labs focus on development of techniques useful in high-incidence crimes, such as burglary and street assault. A probLem of increasing frequency is detecting expls gr other materials before they are used... 

Trace Evidence. Trace evidence refers to minute, sometimes microscopic material found during the examination of a crime scene or a victim s or suspect s clothing. Trace evidence often helps police investigators develop connections between suspect and victim and the crime scene. The challenge to the forensic scientist is to locate, collect, preserve, and characterize the (race evidence. 

To affirm these things, however, is not to raise a valid objection— moral or otherwise—to the scientific investigation of a crime held to be unique and unparalleled in the history of mankind. Even a crime that is alleged to be uniquely reprehensible must be open to a procedure that is standard for any other crime namely, that it can be—must be—subject to a detailed material investigation. Further whoever pos-... 

Certainly Speer, believing that should such an attack be launched in 1945 it would cause the Allies to retaliate in kind, had been going to great lengths to divert raw materials away from the chemical warfare factories.28 As he later testified at the Nuremberg War Crimes Trials in 1946 ... 

The major question posed now is how can soils be used to make accurate forensic comparisons when we know that soils are highly complex and that there are thousands of different soil types in existence For example, according to the USDA, which collects soil data at many different scales, there are more than 50,000 different varieties of soil in the United States alone. Parent material, climate, organisms, and the amount of time it takes for these properties to interact will vary worldwide. First of all, soil samples must be carefully collected and handled at the crime scene and then compared by a soil scientist with forensic science experience to ensure that the soil samples can be useful during an investigation. 

A new rapid mid-infrared spectroscopic method called diffuse reflectance infrared Fourier transform spectra (DRIFTS), coupled with chemometrics, has been developed by Janik, Merry, and Skjemstad (1998) and routinely applied to rapidly screen and compare crime scene samples (Figure 1.1). Added to these rapid methods and techniques are the use of rapid mass and volume magnetic susceptibility methods, which should also always be used before moving to the more costly methods (Figure 1.1). Mineral magnetic techniques are a relatively recent development (post-1971) and have now become a very powerful and widely used research tool to characterize natural materials in landscapes (e.g., Thompson and Oldfield 1986). 

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