The identification of blood and forensic serological studies for species deter- mination, grouping, genetic marker and DNA individualization are utilized in conjunction with bloodstain interpretation and are often mutually bene- ficial to the reconstruction of a crime scene. Both disciplines are important sources of physical evidence. In some cases the bloodstain interpretation may provide more valuable information, whereas in others the serological studies may be more revealing and informative. The value of each should be consid- ered when the investigator is preparing to remove bloodstained objects and individual stains from the crime scene for submission to the laboratory. It is of ultimate importance to photograph and document adequately the location, size, and shape of bloodstains prior to their collection and removal from the crime scene.
The extent of ABO grouping, testing of genetic markers and DNA analysis in bloodstains that is possible in a given case depends on many factors including the age of the blood, the quantity of the blood available, the envi- ronmental conditions to which the blood has been exposed, and the degree of contamination that has occurred. Generally, with a limited sample available and with older samples, fewer systems can be tested. Exposure of the blood to extreme heat is detrimental. Also, it should be recognized that laboratories differ in their abilities and techniques to individualize dried bloodstains. Hospital and clinical laboratories are better equipped to individualize fresh blood in blood banks for transfusion and in cases involving paternal disputes. Many forensic laboratories have developed sophisticated techniques for the individualization of dried bloodstains. Occasionally, the surface upon which the blood has been deposited may provide a source of contamination and limit the extent of blood individualization, for example, on soiled clothing, floors, and vehicle exteriors where large deposits of crushed insects have accumulated. In all cases it is mandatory to collect, for comparative purposes, a negative control sample from an unstained area on the same surface from which the bloodstain is to be collected.
Putrefied blood presents many problems for the serologist because of the contaminating effect of bacteria, fungi, and the enzymatic breakdown of blood components and often produces misleading or inconclusive testing results. Blood may decompose if not packaged properly. For this reason, bloodstained articles should not be packaged wet or sealed in airtight plastic bags which may accumulate moisture. Individual packaging of completely dry bloodstained articles in clean paper bags is most desirable. Crusts and scrapings of bloodstains may be packaged in clean, folded paper or clean plastic containers. It is important during the collection process not to handle bloodstains or control areas with hands or fingers which may contaminate the samples with the blood group substances of the collector if that person is a secretor. All items should be properly labeled and identified for chain of custody purposes.
The following general guidelines are recommended to help ensure opti- mal results in the proper collection and preservation of bloodstain evidence. Investigators should consult with the specific forensic laboratory in order to follow particular protocols and to resolve the issues that may arise.
1. If there is a sufficient quantity of wet, pooled blood at a scene, approx- imately 5 to 10 ml should be collected with a pipette or medicine dropper and placed into a glass tube containing preservative and anti- coagulant. Appropriate tubes containing sodium fluoride and potas- sium oxalate to preserve blood samples are available commercially or
may be provided by the laboratory. Always check with the laboratory personnel for their preference of blood preservative for specific pro- cedures. The wet blood samples should be refrigerated prior to sub- mission to the laboratory.
2. A moist bloodstain on a nonabsorbent surface such as glass or metal may be collected by adding a small amount of sterile physiological (0.9%) saline to the stain and mixing it thoroughly with an applicator stick and retrieving it with a pipette or medicine dropper. A control sample should be collected in a similar fashion. Both should be refrig- erated.
3. Water or other liquids to be tested for blood should be placed into clean jars or other leak-proof containers and refrigerated.
4. When feasible, the entire bloodstained article or object should be collected as evidence after the bloodstains have thoroughly dried and their locations have been photographed and properly documented. 5. Do not fold wet clothing or bedding and do not package it in a wet
condition. When bloodstained sheets, blankets, or pillow cases are removed from a bed or other location, it is important to document top, bottom, left side, right side, and which surface is up or otherwise folded as it was at the scene. Clothing and bedding items should be suspended in a clean area for drying purposes over clean paper to collect any trace evidence that may become dislodged during the dry- ing process. Do not use a hair dryer or heating element to hasten drying. The papers under the dried items should be folded and sub- mitted with the individual articles. The items should be folded and packaged individually in order not to further disturb the bloodstains. 6. Rugs or carpets may be lifted and removed in their entirety in many cases. If this is not feasible, the bloodstained portions and control areas should be cut and removed after photography and proper documen- tation and then packaged in clean paper.
7. If it is not feasible or practical to submit the entire bloodstained surface or object, the bloodstains may be scraped with a clean scalpel or razor blade onto clean paper. To avoid cross-contamination, individual dis- posable blades should be used. Be sure to scrape control surfaces as well. The papers may then be folded, taped and properly identified or transferred to clean plastic containers for submission to the laboratory. 8. If collection of a bloodstain by scraping is not desirable, as with a thin smear on a surface or a bloodstain absorbed into a rough surface such as concrete, it may be best removed by wetting the stain with physio- logical (0.9%) saline and collecting it with a pipette or medicine drop-
per and placing into a clean, glass tube and refrigerating. Control samples should be collected in a similar fashion.
9. An alternative method for the removal and collection of dried blood- stains from smooth surfaces is to moisten a sterile cotton swab or swatch with a physiological (0.9%) saline and rub the stain from the surface. A control sample should be collected in a similar fashion and the samples refrigerated or frozen.
10. Collection of blood samples from the victim at the time of postmortem examination is within the protocol of the medical examiner or forensic pathologist. Consultation with the pathologist will help ensure that sufficient blood is obtained for all procedures necessary, including the toxicological and serological studies. The blood should be collected in separate tubes for each purpose with the appropriate preservatives and anticoagulants.
11. Authority for collection of blood samples from suspects or defendants is obtained through appropriate legal procedures. The forensic labo- ratory that will test the samples should be consulted to ensure that proper samples are collected by a physician, registered nurse, or licensed medical technologist with the proper rules of chain of custody observed in each case.