Crime scene

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. 

B. A. J. Fisher, Techniques of Crime Scene Investigation, 5th ed., Elsevier Science Publishing Co., Inc., New York, 1992. 

Fluorescence Microscope. A useful light microscope utilizes UV light to induce fluorescence in microscopic samples (40). Because fluorescence is often the result of trace components in a given sample rather than intrinsic fluorescence of the principal component, it is useful in the crime laboratory for the comparison of particles and fibers from suspect and crime scene. Particles of the same substance from different sources almost certainly show a different group of trace elements. It is also very useful in biology where fluorescent compounds can be absorbed on (and therefore locate and identify) components of a tissue section. 

Perhaps the most common and well-publicized use of DNA fingerprinting is that carried out by crime laboratories to link suspects to biological evidence— blood, hair follicles, skin, or semen—found at a crime scene. Thousands of court cases have now been decided based on DNA evidence. 

I been established to serve as a registry of convicted offenders. When a DNA sample is obtained from a crime scene, the sample is subjected to cleavage with restriction endonucleases to cut out fragments containing the STR loci, the fragments are amplified using the polymerase chain reaction, and the sequences of the fragments are determined. 

Even the police make use of acids and bases to catch criminals. For example, forensic scientists can compare soil pH found at a crime scene with trace amounts of soil found on a tire tread or shoe bottom. They also use a mixture of hydrogen peroxide and phenolphthalein called Kastle-Meyer solution to test for blood. Kastle-Meyer solution is used at a crime scene when crime scene specialists find spots they suspect could be dried blood. The solution turns bright pink in the presence of blood. If the spots turn out to be something else, such as dried tomato sauce or reddish-brown paint, the Kastle-Meyer solution remains colorless. 

Federal response teams cannot be on site in time to save lives or treat victims. Local response personnel need, but cannot afford, the same assets and training as federal employees are now receiving. Haz-Mat mitigation is a local responsibility. Someone must be on scene at once to isolate the area of a chemical or biological agent attack, evacuate, and care for the injured and the dead, and deny further entry. Any and every chemical or biological attack will be a crime scene that has to be isolated and guarded. 

Gather important information the agent used was it aerosol, liquid, gas, powder or vapor location method of delivery do you have the necessary personal protective equipment (PPE) to deal with the hazard, or have you called for assistance by a specialized team are you sure that anyone who enters a contaminated area has the proper PPE and is trained in its use be sure to establish control — keep all victims, non-victims and bystanders at the crime scene (if there is any suspicion of an attack) until it is determined who among them may be a terrorist or a witness perform decontamination, triage if necessary, isolation, quarantine, search and locate evidence, maintain chain of control, and collect samples. 

In criminal cases, the availability of readable fingerprints is often critical in establishing evidence of a major crime. It is necessary, therefore, to follow proper procedures when taking fingerprints. In major cases, prints should be obtained from all persons who may have touched areas associated with a crime scene, for elimination purposes. 

It is unlikely that a victim of a terrorist attack will use the information in Table 3.2. This information may, however, be useful to emergency responders and medical personnel during triage to identify the most highly exposed individuals. The information may also be useful to postattack investigators who must reconstruct the crime scene and estimate doses to all potential victims. 

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. 

The newer applications involve the field of biotechnology. Proteins produced by genetically altered organisms such as bacteria must be examined to verify that they are identical to the same proteins produced by humans. Also, analysis of DNA from crime scenes is relatively recent. Indeed, DNA analysis and fingerprinting are powerful tools in modern forensics. 

Upon completion of site characterization activities, the team should prepare to exit the site. At this stage, the team should make sure that they have documented their findings, collected all equipment and samples, and resecured the site (e.g., locked doors, hatches, and gates). If the site is considered to be a potentially hazardous site or crime scene, there may be additional steps involved in exiting the site. 

Evidence should not be handled except at the direction of the appropriate law enforcement agency. Specially trained teams from the law enforcement community are best suited (and may be jurisdictionally required) for the collection of physical evidence from a contaminated crime scene. 

The collection of physical evidence is not generally considered time sensitive however, site characterization and sampling activities are time sensitive due to the public health implications of contaminated environmental media air, water, and/or soil. Thus, collection of environmental media samples may precede collection of physical evidence, and care must be taken not to disturb the crime scene while performing these activities. If samples can be collected outside of the boundaries of the suspected crime scene, this may avoid concerns about the integrity of the crime scene. 

Z. Crime scene preservation training and plans AA. Communication plans ... 

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