Crime Scene Investigation: CRIME SCENE SEARCH AND EVIDENCE COLLECTION
The crime scene search should be methodical and performed in a specific pattern. The choice of pattern may be dictated by the location, size, or conditions of the scene. Typical patterns are spiral, strip or lane, and grid and are shown in Figure 2.5. Adhering to the selected pattern prevents “bagging and tagging” random items with no organization or system. Measurements showing the location of evidence should be taken with each object located by two or more measurements from non-movable items, such as doors or walls. These measurements should be taken from perpendicular angles to each other to allow for triangulation. Be alert for all evidence: The perpetrator had to enter or exit the scene! Mark evidence locations on the sketch and complete the evidence log with notations for each item of evidence. If possible, having one person serving as evidence custodian makes collection more regular, organized, and orderly. Again, if possible, two per sons should observe evidence in place, during recovery, and being marked for identification. Use tags, or if feasible, mark directly on the evidence. Wear gloves to avoid leaving fingerprints—but be aware that after about 30 min, it is possible to leave fingerprints through latex gloves! Evidence should not be handled excessively after recovery. Seal all evidence packages with tamper-evident tape at the crime scene. An important activity often overlooked is the collection of known standards from the scene, such as fiber samples from a known carpet or glass from a broken window. Monitor the paperwork, packaging, and other information throughout the process for typographic errors, clarity, and consistency. Simple geometry can help locate and reconstruct where things were in a sketch. Always take measurements from at least two locations. This will help with check ing distances and triangulating “untaken” measurements later. In trigonometry and elementary geometry, triangulation is the process of finding a distance to a point by calculating the length of one side of a triangle, given measurements of angles and sides of the triangle formed by that point and two other reference points. In many ways, measuring a crime scene is surveying, the art and science of accurately deter mining the position of points and the distances between them; the points are usually on the surface of the earth. Surveying is often used to establish land boundaries for ownership (such as buying a house) or governmental purposes (geographic surveys). Large crime scenes may require standard surveying (and the prepared CSI would do well to learn a bit of surveying), but processing an indoors crime scene is much the same except for issues of points (guns, not mountains) and scale (inches, not miles).
FIGURE 2.5 It is best to have an organized systematic search of a crime scene. The strip (or lane), the spiral, and the grid are three of the most common patterns.
