Physical Evidence and Collection Methods

The paper discusses what physical evidences are in relation to criminology, examples of physical evidences, and how they are used in trial. It further describes how to collect some few examples of these evidences and how they are preserved before they are taken to the laboratory for examination. There are standard collection procedures for each sample and these procedures have to be adhered to for the evidence to be of benefit for the purpose it is intended for.

Physical evidence is any evidence that is left behind at the crime scene. It can also be described as any evidence introduced in a trial in the form of a physical object, aimed at proving a fact in the issue based on its demonstrable physical features. It can be whole or a portion of any object. Examples of physical evidence can include biological materials left at the crime site such as hairs and blood, weapon used by the attacker, and blood stains. These evidences are used to link the suspect to the crime. Here below are examples of physical evidences, how they are collected and preserved (Fallis, 1998).

Blood stains
Blood can be found as either a pool or stains on clothing or on the ground. A pool of blood is sampled by use of a sterile gauze pad or cloth and then air dried at room temperature. It can then be preserved by a way of refrigeration or frozen immediately and transported to the laboratory. If the sample is delayed for more than 48 hours, it is likely to deteriorate before analysis therefore rendered useless. In situations where the laboratory is near, blood stained objects can just be delivered immediately without preservation (Fisher, 2004).

In situations where laboratory is far and the material has to be mailed, it should be allowed to dry completely before it is packed. The process of drying should not be done either by heating or under sunlight, but should be done in a room with adequate ventilation. Dried blood stains found on clothing should be rolled in a brown paper bag or box, sealed, and labeled. Avoid removing the blood stains from the clothing (Flynn, 2009). When the stain is on small solid objects, the whole object should be sent to the laboratory after it has been labeled and packaged.

In some situations, the stain can be found on a large object. The stained area should be protected by a sterile paper with the edges of the paper sealed with a tape (Fallis, 1998). If it is not possible to take the whole object to the laboratory, the stain should be scraped off and placed in a clean piece of paper which can be placed into an envelope. When scraping off the blood stain, a sterile dry knife or another object should be used. Each stain should be scraped separately and placed on different packages (Flynn, 2009).

Human hair can be examined to reveal the race of the individual from which it came from and also from which part of the body. By comparing two types of hairs, one is able to ascertain whether they came from one person or from different individuals. They are normally examined depending on the amount collected and the features realized at examination.

In a crime scene, all hair present should be collected. They can be collected by use of fingers or tweezers to pick them up and place in paper bags or envelopes. These envelopes are then sealed and placed in larger ones (Fisher, 2004). The outer envelope should then be sealed. In some cases, hair can be found attached to dry blood or trapped in a metal or crack of glass. If the object where the sample is stuck is small, it can be marked, wrap, and sealed in an envelope. If it is large, the area where the hair is stuck should be wrapped. This prevents the loss of hair during transport to the laboratory (Flynn, 2009).

In cases of rape, the pubic hair of the victim is combed before collecting the standard samples. The unknown hair sample is then compared with the hair from the victim, suspect or sample from any other source (Fallis, 1998). This would mean that sample is collected from the victim, suspect, and from other related sources. Head hairs are collected by letting the person bend over a clean sheet of paper. They are then instructed to run their hands through the hair so that some loose hair can be obtained. More samples can be obtained by plucking off from the representative areas of the head. About 50 to 100 strands of hair are recommended. While collecting the sample, it should not be cut. The same method is applied when collecting samples from other parts of the body. When collecting samples from the pubic area, about 30 to 60 strands are required. When collecting from a suspect, hair should be collected from all parts of the body (Fisher, 2004).

Seminal stains
These are frequently collected from the clothing, sheets, and blankets. The stains are air dried, wrapped in a clean piece of paper and sealed in a paper bag. Plastic packages should be avoided when packing this type of specimen. In cases of sexual offenses, the victim should be examined by the doctor who would then collect evidence from the victim by using sexual assault evidence kit (Fisher, 2004). The kit has instructions which should be adhered to. Other evidences such as under shorts, panties, or others be labeled and packed separately. If the samples are still wet, they should be allowed to dry completely before they are packed. There should also be minimal handling of fabrics used as evidence.


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