Collection and Preservation of Blood Evidence at a Crime Scene Research Paper
- Length: 5 pages
- Sources: 5
- Subject: Criminal Justice
- Type: Research Paper
- Paper: #72681740
Excerpt from Research Paper :
A POTENTIAL AND VALUABLE LINK
Blood evidence is an extremely valuable item in criminal justice (Schiro, 2011; NIJ, 2000; OSP, 2002; NFSTC, 2013; Bestino, 2013). It has the unique and undisputable potential of solving a case or a crime as it can accurately identify a participant or a victim in a crime. It can form a connection between a person and a criminal act, enhance or contradict a testimony. It sets the investigator's direction in solving the case. When blood evidence is carefully documented, collected and stored, it can be presented in court even after a number of years from the time of the commission of a crime. Most importantly, blood evidence has the potential of pinning a particular suspect down or eliminating him (Schiro, NIJ, OSP, NFSTC, Bestino).
The Role of Communication
In order to assure that the collection and preservation of this very essential item, open communication should be established between the crime scene investigator and the forensic scientist (Schiro, 2011; Bertino, 2013; NIJ, 2002; OSP, 2002; NFSTC, 2013). The investigator should be thoroughly familiar with the capabilities of the crime lab, its preferred blood collection and preservation methods, the relevant investigative information to the forensic scientist, and the type of reference samples the crime lab requires. Investigative information can change with technology, lab policies, lab personnel or administration. A forensic investigator may also prefer a particular method of collection. It is then advisable for the investigator to confer regularly with forensic scientists for the suitable and agreed method for efficient collection and preservation (Schiro, NFSTC, NIJ, OSP, Bertino).
The investigator first determines the potential value of the blood evidence found and all potential problems in documenting, collecting and preserving it (Schiro, 2011). Some problems may be a lack of communication often between the investigators and forensic scientists; their lack of familiarity the types of bloodstain analysis; a lack of knowledge in determining the stains to collect for a maximum of useful information; poor or good reference samples; and the indiscriminate use of luminal in crime scenes. Luminol is a chemical, which can make bloodstains glow in the dark (Schiro).
Blood evidence is usually present in violent and property crimes in the form of bloodstains (OSP, 2002). Bloodstains may be red, brown, tan or yellowish. They are often undetectable to the un-practiced eye. Blood is a valuable indicator of DNA, cells and proteins, which can be examined to identify the perpetrator or victim. Tests will determine if blood is present in the stain and if the blood is human or non-human (OSP).
Collecting liquid or moist blood has two separate procedures, depending on the quantity (OSP, 2002). If the blood evidence to be collected is in large quantity, the collector should saturate 4-6 sterile cotton swabs with the evidence. He should collect a good mix of clot cells and serum. The swabs should thoroughly air dry then placed in a paper container. Then the container should be properly labeled and sealed. If in small quantity, there should only be a limited number of swabs. Use them to collect the blood one-by-one. They should also thoroughly dry, placed in a paper container, properly labeled and then sealed. If the bloodstained object can be moved, the whole item should be submitted intact. If not transportable, the blood may be collected by swabbing or cutting out the stain. Cutting out the stain is preferable if it has dried on an object like the upholstery of a car seat or carpet. A clean and sharp knife or scissors can be used to excise the stained area. The collector must be careful to include unstained surrounding as a substrate control and to prevent stain contamination. It should be packed in a paper container and then properly labeled and sealed like other pieces of evidence (OSP). Other methods are scrapping and lifting with a tape (NFSTC, 2013). Scrapping involves the use of a clean razor blade or scalpel. The evidence sample is scraped into a clean piece of paper, which can later be folded and packed in a paper envelope or another package. Dried blood stains may be collected with the use of fingerprint lifting tape. The tape is placed over the stain and then lifted. The stain is then transferred into the adhesive side of the tape. It can thus be taken and transferred into a clear piece of acetate and submitted to the laboratory (OSP).
Processing of Blood Evidence
This phase begins after the crime scene is thoroughly documented and the location of evidence has been established (Bestino, 2013; NFSTC, 2013; NIJ, 2000; OSP, 2002; Schiro, 2011). The most perishable evidence is usually collected first, especially that which has to be moved or transferred. Lots of photographs should be taken to document what could have been missed. Most pieces of evidence are collected in clean and un-used containers like packets, envelopes and bags. Wet or moist biological evidence, such as blood, body fluids and plants, are usually places in these containers at the scene and brought to a receiving area if storage is less than two hours. This is to prevent contamination by other evidence there. These wet or moist pieces of evidence in whatever package should be removed from the location and allowed to air dry completely. When dried, they should be placed in new, clean and un-used dry paper containers. Moist evidence should not be sealed in a plastic or paper container for more than 2 hours. Microorganisms tend to grow in moist environments and destroy or create changes in the evidence. Different pieces of evidence in a common location may also cross contaminate one another and should, therefore, be packed separately. The containers should be closed properly and kept securely away from the others to prevent their mixture while in transport. Each container should be completely and properly labeled. It should have the collecting person's initials, the date and time of collection, a complete description of the evidence, where found, and the investigating agency and file number (Bestino, NFSTC, NIJ, OSP, Schiro).
The investigator should first check out on loose trace evidence, such as hairs, fibers, pain chips and the like, before the items are transported (Bestino, 2013; NFSTC, 2013; NIJ, 2000; OSP, 2002; Schiro, 2011). These should be collected in a packet and into an envelope as they may get lost during transport. The envelope should be labeled with the complete information of these traces as to description and sources. Blood evidence should be kept from extreme heat and humidity. Bloodstained items should be stored in a refrigerator until transported to the crime laboratory. Persons handling these sensitive pieces of evidence should wear protective clothing, globes, masks and eye protection when necessary (Bestino, NFSTC, NIJ, OSP, Schiro).
The admissibility of evidence in court depends on the continuous chain of custody from the laboratory to the courtroom (NFSTC, 2013). This continuity is premised on the assumption that the evidence presented in court is the same found and gathered from the scene of the crime. The access to it must also be adequately controlled and properly documented (NFSTC). The chain of custody begins with the person who finds the evidence (NIJ, 2000; Bertino, 2013). He marks it for identification and places it in a plastic or paper container. The last container is a collection bag, properly labeled with all the pertinent information. It is sealed with the collector's signature across the sealed edge. This container passes on to the next person responsible. He takes it to the lab, signs it and turns it over the technician. The technician opens and examines the package from a point other than the sealed edge. When finished, the technician repackages the evidence with the original container. He re-seals it in a new package and then signs the log…