The integrity of evidence is best maintained when the item is kept in its original condition as found at the crime site. Whenever possible, evidence should be submitted to the laboratory intact. Blood, hairs, fibers, soil particles, and other types of trace evidence should not normally be removed from garments, weapons, or other articles that bear them. Instead, the entire object is to be sent to the laboratory for processing. Of course, if evidence is adhering to an object in a precarious manner, removing and packaging the item best exercise good judgment. If evidence is found adhering to large structures, such as a door, wall, or floor, common sense must be used; remove the specimen with a forceps or other appropriate forensic tool. In the case of a bloodstain, one has the option of either scraping the stain off the surface, transferring the stain to a moistened swab, or cutting out the area of the object bearing the stain.

Each different item or similar items collected at different locations must be placed in separate containers. Packaging evidence separately prevents damage through contact and prevents cross-contamination.

The well-prepared evidence collector will arrive at a crime scene with a large assortment of packaging materials and tools ready to encounter any type of situation. Forceps and similar tools may have to be used to pick up small items. Unbreakable plastic pill bottles with pressure lids are excellent containers for hairs, glass, fibers, and various other kinds of small or trace evidence. Alternatively, envelopes, screw-cap glass vials, or cardboard pillboxes are adequate containers for most trace evidence encountered at crime sites. Ordinary mailing envelopes should not be used as evidence containers because powders and fine particles will leak out of their corners. Small amounts of trace evidence can also be conveniently packaged in a carefully folded paper, using what is known as a “druggist fold”. This consists of folding one end of the paper over one-third, then folding the other end (one-third) over that, and repeating the process from the other two sides. After being folded in this manner, the outside two edges are tucked into each other to produce a closed container that keeps the specimen from falling out. Although pill bottles, vials, pillboxes, or manila envelopes are good universal containers for most trace evidence for forensic document examination, two frequent finds at crime scenes warrant special attention. If bloodstained materials are stored in airtight containers, the accumulation of moisture may encourage the growth of mold, which can destroy the evidential value of blood. In these instances, wrapping paper, manila envelopes, or paper bags are recommended packaging materials. As a matter of routine, all items of clothing are to be air-dried and placed individually in separate paper bags to ensure a constant circulation of air through them. This will prevent the formation of mold and mildew. On the other hand, charred debris recovered from the scene of a suspicious fire must be sealed in an airtight container to prevent the evaporation of volatile petroleum residues. New paint cans or tightly sealed jars are recommended in such situations.

Assigning those responsible for searching a crime scene is a function of the investigator in charge. Except in major crimes, or where the evidence is very complex, it is usually not necessary to have the assistance of a forensic scientist at the crime scene to perform Forensic Document Examination, his or her role appropriately begins with the submission of evidence to the crime laboratory. As has already been observed, some police agencies do have trained field evidence technicians to conduct the search for physical evidence at the crime scene. They have the equipment and skill to photograph the scene and examine it for the presence of fingerprints, footprints, tool marks, or any other type of evidence that may be relevant to the crime. An investigator proceeds to carry out a crime-scene search depending on the setting and size of the area, as well as on the actions of the suspect(s) and victim(s) at the scene. It is advisable to have one person supervising and coordinating the collection of evidence. Without proper control, the search may be conducted in an atmosphere of confusion with needless duplication of effort. Evidence collectors may choose to subdivide the scene into segments and search each segment individually, or the search may start at some outer point and gradually move toward the center of the scene in a circular fashion. The areas searched must include all probable points of entry and exit used by the criminals. What to search for will be determined by the particular circumstances of the crime. Obviously, the skill of crime-scene investigators at recognizing evidence and searching relevant locations is paramount to the successful processing of the crime scene. While training will impart general knowledge for conducting a proper crime-scene investigation, ultimately the investigator must rely on the experience gained from numerous investigations to formulate a successful strategy for recovering relevant physical evidence at crime scenes. In the case of a homicide, the search will be centered on the weapon and any type of evidence left as a result of contact between the victim and the assailant. The cross-transfer of evidence, such as hairs, fibers, and blood, between individuals involved in the crime is particularly useful for linking suspects to the crime site and for corroborating events transpiring during the commission of the crime. During the investigation of a burglary, efforts will be made to locate tool marts at the point of entry. In most crimes, a thorough and systematic search for latent fingerprints is required.Vehicle searches must be carefully planned and systematically carried out. The nature of the case determines how detailed the search must be. In hit-and-run cases, the outside and undercarriage of the car must be examined with care. Particular attention is paid to looking for any evidence resulting from a cross-transfer of evidence between the car and the victim-this includes blood, tissue, hair, fibers, and fabric impressions. Traces of paint or broken glass may be located on the victim. In cases of homicide, burglary, kidnapping, and others, all areas of the vehicle, inside and outside, are searched with equal care for forensic document examination and physical evidence. Physical evidence can be anything from massive objects to microscopic traces. Often, many items of evidence are obvious in their presence, but others may be detected only through examination in the crime laboratory. For example, minute traces of blood may be discovered on garments only after a thorough search in the laboratory, or the presence of hairs and fibers may be revealed in vacuum sweepings or on garments only after close laboratory scrutiny. For this reason, it is important to collect possible carriers of trace evidence in addition to more discernible items. Hence: it may be necessary to take custody of all clothing worn by the participants in a crime. Clothing item should be handled carefully and wrapped separately to avoid loss of trace materials. Critical areas of the crime scene should be vacuumed and the sweepings submitted to the laboratory for analysis. The sweepings from different areas must be collected and packaged separately. A portable vacuum cleaner equipped with a special filter attachment is suitable for this purpose. Additionally, fingernail scrapings from individuals who were in contact may contain minute fragments of evidence capable of providing a link between assailant and victim. The undersurface of each nail is best scraped with a dull object such as a toothpick to avoid cutting the skin. These scrapings will be subjected to microscopic examination in the laboratory. The search for physical evidence must extend beyond the crime scene to the autopsy room of a deceased victim. Here, the medical examiner or coroner will carefully examine the victim to establish a cause and manner of death. As a matter of routine, tissues and organs will be retained for pathological and toxicological examination. At the same time, arrangements must be made between the examiner and investigator to secure a variety of items that may be obtainable from the body for laboratory examination. The following are to be collected and sent to the forensic laboratory: (1) Victim’s clothing (2) Fingernail scrapings (3) Head and pubic hairs (4) Blood (for typing purposes) (5) Vaginal, anal, and oral swabs (in sex-related crimes) (6) Recovered bullets from the body (7) Hand swabs from shooting victims (for gunshot residue analysis) Once the body is buried, efforts at obtaining these items may prove difficult or futile. In addition, a lengthy time delay in obtaining many of these items will diminish or destroy their forensic value. In recent years, many police departments have gone to the expense of purchasing and equipping “mobile crime laboratories” for their evidence technicians. However, the term mobile crime laboratory is a misnomer. These vehicles carry the necessary supplies to carry out the functions of a chemical laboratory. Crime-scene search vehicle would be a more appropriate but perhaps less dramatic name for such a vehicle.

Physical evidence covers any and all objects that can establish that a crime has been committed or can provide a connection between a crime and its victim or a crime and its suspect. If physical evidence is to be effectively used for assisting the investigator, its presence first must be recognized at the crime scene. If all the natural and commercial objects within a reasonable distance of a crime were gathered so that the scientist could discover significant clues from them, the overflow of material would quickly immobilize the laboratory facility. Physical evidence can only achieve its optimum value in criminal investigations when its collection is performed with selectivity done by the collector’s thorough knowledge of the crime laboratory’s techniques, capabilities, and limitations. Even though it is true that present-day technology has given the crime laboratory capabilities far exceeding those of past decades, these advances are no excuse for contentment on the part of criminal investigators. Crime laboratories do not solve crimes; only a thorough and competent investigation conducted by professional police.