The collection of evidence starts immediately after the investigator identifies and documents the crime scene (Karagiozis, 2005). Generally, the easy to lose pieces of evidence, fragile and any evidence that needs to be moved should be collected first. Since other forms of evidence may not be correctly documented, the investigator should reinforce the evidence with photographs. In this case, the investigator is supposed to recover dried blood, hand held hairs, shell casings as well as a handgun in a crime scene involving a deceased victim. Dried blood may be obtained from a small or a big object; if the investigator finds it on a small object, the whole object should be properly labelled, packaged and taken to the laboratory for testing. Where the big object is transportable, the investigator has to properly cover the stained part using some piece of paper and a tape to prevent contamination while transporting the object to the lab. If however the big object is not transportable, the stained area needs to be cut, labelled ant taken to the laboratory (Drielak, 2004).
A finger print tape is also used in lifting the stained sample but the investigator must be cautious to avoid touching the sticky part. A clear tape is widely used to recover visible hair from the hands of a victim in a crime scene. The investigator should consider using a less sticky tape to avoid clogging it with fiber. It is the responsibility of the investigator to ensure personal safety as well as safety of the custodians of the evidence when recovering a handgun from the crime scene. Sturdy boxes are the most commonly used collection mediums in recovering firearms. The box is designed with numerous slits at the bottom in order to secure the handgun during transportation (Drielak, 2004). If shell casings are found in a crime scene, they are recovered and preserved in a similar manner as firearms. Shell casings are excellent indicators of the gun type used to execute the crime.
Paper containers including bags, packets and envelopes are often used in collecting liquid evidence. However, the containers must be leak proof and not breakable. While arson evidence is collected with an air-tight and clean metal jar, plastic bags are used in collecting huge quantity of dry powder evidence. Wet evidence is collected with plastic containers but it should be transported to the receiving area within two hours. Once received, the wet evidence is then removed from the container and allowed in dry air. If it is packaged in a plastic container or bag, Moisture enhances the growth of other microorganism that destroys the evidence. Items that are capable of cross contamination are separately packaged (Karagiozis, 2005). The investigator must remember to secure and close the containers to avoid mixture of evidence when transporting. Furthermore, the containers must hold a full description of the evidence including the initials of the person collecting it, time and date of collection, location, and the name of the investigator or the agency.
Maintaining and preserving evidence collected in a crime scene is critical. It begins with selecting packaging tools of the right material and size. Each evidence should be should be kept separately, labelled well, sealed and properly documented. Small pieces of evidence must be carefully packaged because they are easily lost. Electronic evidence need to be specially treated. Cell phones for instance should be maintained in special bags capable of blocking signals as well as protecting them from static electricity. Such bags are also used in preserving computers and other electronic devices (Drielak, 2004). Specially made plastic containers are ideal for maintaining sharp evidence such as glasses and syringes that are risky. Knives and firearms are placed in sturdy boxes that straps them without destroying the evidence. Where any of these pieces of evidence contain bloodstains or other fluids, the investigator must insert a biohazard label in the outer part of the packaging. In some cases, gloves are used in collecting evidence but the investigator must be careful to avoid wiping any prints that were originally available in the object.
Some crimes take seconds, others minutes while others take hours but all these are solved by either serological tests, DNA forensic tests, drug chemistry tests and other tests performed in crime labs. Serology tests is the type of test done to identify body fluids available in the evidence. Serological fluids are drawn from saliva, feces, blood, semen as well as vagina of the victim (Karagiozis, 2005). DNA tests are widely applied tests especially in determination of cases in courts of law. Drug chemistry tests are used in identifying as well as quantifying the use of controlled drugs. Drug chemistry tests are performed using numerous distinct and separate technologies.
In summary, various guidelines for proper collection, maintenance and preservation of evidence exist to help investigators perform accurate investigations. The objective of proper collection, use of the right tools and conducting the right tests is to reconstruct crimes, identify the victims and prepare the evidence in a manner that can be applied in courts of law in determination of cases.
References
Drielak, S. C. (2004). Hot Zone Forensics: Chemical, Biological, and Radiological Evidence Collection. Springfield: Charles C Thomas Publisher, LTD.
Karagiozis, M. F. (2005). Forensic investigation handbook: An introduction to the collection, preservation, analysis and presentation of evidence. Springfield: Charles C Thomas Publisher, LTD.