6 Body Fluid Stains and Standards

Transcription

1 6 Body Fluid Stains and Standards Laboratory examination of body fluids (i.e., blood, semen, saliva, etc.) may produce significant information in certain investigations. This chapter considers the recognition, collection, and preservation of some of these commonly encountered forms of biological evidence. I. Bloodstains and Blood Standards In crimes of violence, blood is usually found in the form of dried stains. Blood can frequently be identified and genetically compared to blood standards from individuals if a sufficient quantity is properly collected and submitted. In addition to identification and comparison testing, the shape and pattern of the bloodstaining may provide information concerning how the blood was deposited. A. Bloodspatter Pattern Analysis The examination of bloodstain patterns has always been a part of crime scene investigation, but it seems to have gained more emphasis in recent years as a separate discipline. Careful observation, measurement, and documentation of the size, shape and pattern of bloodstains can reveal significant information in some cases, e.g., direction and angles of bloodspatter, origination point(s), and the minimum number of blows in a beating or stabbing incident. When there may be special relevance to the bloodspatter found at a scene, it is essential to preserve those patterns until someone trained in the examination of bloodspatter patterns can examine them. Although photography is useful in the recording of some of the aspects of bloodspatter at a crime scene, it does not substitute for a detailed examination. 57

2 6 - Body Fluid Stains and Standards B. Procedure When Blood is Found at the Scene Record the following: a. Physical state (fluid, moist, dry) b. Amount present (few drops, small pool, etc.) c. Shape (smear, round drops) d. Exact location in relation to fixed objects e. Pattern of stains (all in one spot, trail) f. Atmosphere conditions (temperature, humidity) g. Date and time of observation 2. Take scaled and unscaled photographs of stains. 3. Liquid blood: If a pool of fluid blood is present, collect in the following manner: a. Wear gloves, mask and eye protection while soaking up samples. Using cotton swabs, soak the suspected blood onto the swabs. Continue collecting the stain until it is either completely collected or until five swabs have been saturated. Do not touch the swabs with your fingers. Make sure to avoid contaminating your supply of swabs. Change your gloves frequently but change them immediately if you suspect any contamination of your gloves. b. Allow the swabs to dry in place or place them on a nonporous surface like a glass microscope slide and allow to thoroughly air dry. c. Package the dried swabs in a paper container (i.e., white slide box, envelope, paper bag, etc.). Use separate containers for each area recovered. Label the paper container with a biohazard sign. d. Properly label and seal each container. e. Select an unstained area adjacent to the suspected bloodstain and collect a sample from this area as described in 4.a. through 4.d. This sample will serve as a control. Package, label, and seal this control separately from the stained material.

3 4. Dried or moist bloodstain recovery: Body Fluid Stains and Standards - 6 If the stained object is transportable, submit the item intact. If the suspected blood is still moist, allow it to thoroughly air dry in a well ventilated but draft-free area prior to packaging. Label the area with biohazard signs. Package item in a clean paper container, seal and label. (See Chapter 18, Clothing and Fabrics.) If it is impractical to submit the bloodstained item to the Laboratory or it is not possible to cut or remove a portion of the stained and unstained area of the item, then collect in the following manner: a. Wear gloves, mask and eye protection while collecting samples. Moisten a sufficient number of cotton swabs to collect the stain. It is better to underestimate the amount of swabs required as additional swabs can always be used. Wet the swabs using distilled water, or clean tap water if distilled water is not available. Do not touch the cotton with your fingers and do not dilute the stain by using too many swabs or too much water. b. Gently swab the stain with the moistened swabs until the swabs thoroughly absorb the blood and are a dark reddish brown coloration. Continue collecting the stain until it is either completely collected or five swabs have been saturated. c. Allow the stained swabs to thoroughly air dry either directly on the stained object or on a clean glass microscope slide. To avoid contamination, swabs can also be dried by making a small perforation in a pillbox and placing the swab into the perforation. This will allow the swab to dry without contacting any other surfaces. d. Package, label, and seal the air-dried swabs in a paper container (i.e., white slide box, envelope, etc.). Label with a biohazard sign. e. Select an unstained area adjacent to the suspected bloodstain and collect a sample from this area as described in 4.a. through 4.d. This sample will serve as a control. Package, label, and seal this control separately from the stained material. 59

4 6 - Body Fluid Stains and Standards C. Procedure for Collecting Standard Blood Samples from Victims and Suspects Collect at least 5 ml of blood into an EDTA (lavender-top) tube. 2. If alcohol and/or drug analysis is required. Blood samples must be drawn by a licensed physician, nurse, or medical technician using an antiseptic skin towelette (e.g., Zephiran or benzalkonium chloride) to clean the site where the blood sample will be drawn. Draw 20 ml (2 tubes) of blood into grey-top tubes. These tubes contain sodium fluoride and potassium oxalate as a preservative and anticoagulant. These tubes are commercially available and are also found in the OWI Kits. Lavender top tubes may be used if grey-top tubes are unavailable. In some cases, blood is in short supply and toxicology and DNA testing may be required. Toxicology can use DNA specimens but DNA can have difficulty with toxicology blood preservatives. For cases where limited blood is available and DNA and toxicology are to use the same blood sample, lavender-top tubes should be used. II. Saliva Label all tubes and seal them in an appropriate styrofoam container. Store in refrigerator. Label with a biohazard sign on the outside of the box. Saliva stains are not usually evident from a visual examination. However, certain types of evidence frequently contain traces of saliva (e.g., cigarette butts, gummed surfaces of envelopes, stamps, bite marks, areas where oral contact may have occurred, etc.) and sometimes the amount of saliva present is sufficient to determine the DNA type of the individual who is the source of the saliva. A. Procedure for the Collection of Evidential Forms of Saliva 1. Transportable objects Easily transportable objects such as individual cigarette butts and envelopes should be placed in a paper container (i.e., paper bag or envelopes) and the container should be properly labeled and sealed.

5 Body Fluid Stains and Standards Non-transportable objects If transporting the object is not practical, such as in the case of bite marks on the body of sexual assault victims, then the saliva can be collected as follows: a. Moisten a cotton swab with distilled water. b. Shake the swab to eliminate excess water. c. Gently swab the suspected saliva stain. Using a dry swab go over the stained area to absorb any remaining moisture. d. Allow the swabs to thoroughly AIR DRY prior to packaging, labeling, and sealing in a paper envelope. Air drying can be accomplished by making a perforation in the center of a pillbox, inserting the swab into the perforation and allowing the swab to air dry. e. Select an unstained area and collect as in 4.a. through 4.d. Package, label, and seal separately from the stained material. This swab will serve as a control. B. Standards Required to Complete Saliva Comparisons A standard saliva sample is not required to perform saliva comparisons. Standard blood samples are normally used for this purpose. Collect standard blood as described under IC1. III. Seminal Stains Where a sexual offense has occurred, stains may be found on clothing, bedding, rags, upholstery or other objects. Seminal stains can be helpful in establishing whether or not an alleged sexual act occurred and can also provide information concerning the person who contributed the semen. A. Procedure for the Collection of Seminal Stains 1. Carefully recover all suspected stained material including the clothing worn by the victim and the suspect at the time of the offense. Each item of evidence should be packaged separately, labeled and sealed. 61

6 6 - Body Fluid Stains and Standards 2. Air dry all damp stains in a well-ventilated but draft-free area. Clean paper should be spread under the item to catch any debris, which may be dislodged during the drying process. 3. Package, label, and seal each item along with the paper upon which the item dried. Use only paper containers for packaging (i.e., paper bags). 4. If the suspected seminal stain is on an object, which cannot be transported, collect as in II.A.2. B. Standards Required to Complete Semen Comparisons A standard semen sample is not required to perform semen comparisons. Standard blood samples are normally used for this purpose. Collect standard blood as described above in IC1. IV. Other Body Fluids. Vaginal secretions in the form of a foreign DNA (DNA that did not originate from the individual swabbed) can sometimes be attributed to another individual when the penis of a suspected sexual perpetrator is swabbed at the time he is apprehended. The sample is collected by wetting a cotton swab with distilled water and swabbing the external area of the penis. This type of analysis is most successful when the perpetrator is apprehended shortly after the alleged occurrence of sexual activity, generally within twenty-four hours and prior to bathing. The outer area of condoms can also yield this type of DNA. 62