Handling Evidence

A bloodstained article should not be packed for transmittal to the laboratory until it has thoroughly dried. The drying must be a natural process-heat or electric fans should not be used.

If heat is applied to a bloodstain, physical changes will take place within the bloodstain and interfere with its examination in the laboratory. The airstream from a

fan may remove hairs, fibers, or other microscopic particles from the exhibit that might have considerable bearing on the investigation The fan also may blow extraneous material onto the bloodstain.

Clean wrapping paper should be used for packing bloodstained articles. Each bloodstained article should be wrapped individually before it is boxed for transmittal to a criminal investigation laboratory to prevent stains or other microscopic evidence from being transferred from one article to another.

When bloodstained clothing is submitted to the laboratory, the entire garment, where possible, should be transmitted to assure a complete analysis.

If the bloodstain appears on a large object, such as a rug or a drape, the size of which makes its transmittal impractical, the bloodstained area may be removed. However, for control testing, some of the unstained material from around the bloodstain should be included with the stained part.

In all cases, as much of the dried stain as possible should be submitted. Also, a photo of the item detailing the area should be included.

Where bloodstains appear on fixed objects or objects too bulky to transmit to the laboratay, a different procedure should be used. That portion of the object bearing the stain should be cut off and sent to the laboratory, if possible.

Stains on objects that cannot be cut, such as concrete floors or metal safes, are scraped and the crusty portion of the stain collected on a clean piece of paper. The paper is then folded and placed in a vial or other suitable container. A swab is dampened with either saline or distilled water, and the remainder of the stain is taken by rubbing the swab on the stain. Allow the swab to dry, then place it in a suitable container. For control testing, an unstained area adjacent to the bloodstain should also be swabbed, dried, placed in another container, and sent to the lab for comparison.

If a bloodstain appears on a porous article such as wood or earth, the bloodstain, as well as a portion of the material upon which the stain appears, should be removed so proper control tests may be made. The material removed should be placed in a clean pillbox or similar container, properly labeled on the outside with identifying data, and sealed to prevent loss through leakage.

It is often desirable to obtain liquid blood samples from individuals involved in an incident and to forward them to the laboratory with other evidence. Blood samples should be drawn by a medical officer or a trained medical technician at a medical installation where proper precautions may be taken to prevent contamination of the samples.

The quantity of liquid blood required for laboratory examination is approximately 5 cubic centimeters or approximately 1/6 of an ounce. Two tubes of blood should be submitted, one with an anticoagulant and one without. No preservative maybe added to whole blood, as it interferes with subsequent blood tests. If a delay occurs between the time the blood is drawn and the time it can be forwarded to the laboratory for analysis, refrigerate, but do not freeze, the sampling.

Transmittal of Evidence

All types of blood evidence should be forwarded to a laboratory by the fastest means available to prevent deterioration. The quickest means possible usually will be registered mail or a courier who will travel by air. A liquid blood sample should not be packaged with other specimens because, despite precautions taken in packaging, there may be breakage or leakage and consequent contamination of other evidence in the package. It should be forwarded in a sterile, tightly sealed glass container, properly labeled and packaged to prevent breakage.

Laboratory Examination

Preliminary laboratory examinations of an alleged bloodstain use chemical tests to establish if the stain is a bloodstain. If the results are negative, the stain cannot be blood; if the results are positive, further examination and testing are required. The chemical tests used may not be conclusive, because other substances, common chemical compounds, and certain body discharges may also give positive reactions.

After establishing that the stain is a bloodstain, it must be determined if the blood is of human origin. The evidentiary value may be seriously impaired unless the stain is shown conclusively to be human blood. A suspect may claim the blood to be that of an animal that he or she has handled in some way.

The preferred test for human blind is the precipitin test-a complicated laboratory procedure requiring an adequate amount of blood sample. For this reason, transmit as much of the bloodstain as possible to a laboratory. Minimum specimen quantity necessary for this test cannot be stated because reactions vary according to the condition of the specimen. The laboratory approach to the problem will depend upon the size and condition of the bloodstain and the nature of the object upon which the bloodstain appears.

If the specimen is found to be human blood, a determination will be made as to what blood group it belongs. The blood of every human being belongs to one of four blood groups-O, A, B, or AB. This grouping is based on the presence or absence in the blood of group specific substances, either singly or in combination. The blood group is not changed by the lapse of time or by disease.

In the continental United States, the approximate percentage of individuals belonging to group O is 43 percent; to group A, 40 percent; to group B, 12 percent; and to group AB, 5 percent.

Laboratory examination may also determine blood group subgroupings, RH factor, MN grouping, polymorphic proteins, and the presence of some diseases.

Grouping dried bloodstains is considerably more difficult than grouping liquid blood. The age of the dried bloodstain or degree of exposure to direct sunlight, extreme temperatures, or other natural conditions may produce changes that reduce the possibility of successful grouping.

For blood group testing, it is necessary to have more than a small spot of blood. If specimen quantity is limited, the grouping tests may have to be eliminated entirely and the examination limited to chemical and precipitin tests. The more specimen furnished, the greater will be the possibility of obtaining maximum information during laboratory examination.

A fairly heavy bloodstain measuring 1/2 by 1/4 inch is generally sufficient for a conclusive grouping determination. Specimens that do not conform to this size must not be arbitrarily discarded as unworthy of examination.

Eighty percent of the population are secretors, or those whose body fluids such as saliva, perspiration and semen permit accurate typing as to blood group.

Accurate groupings have been made of the saliva found on a cigarette butt. The possibility of using the dried remains of body fluids other than blood should never be overlooked.

Accurate blood grouping depends on the ability of the examiner. The tests demand that the examiner have extensive practice and experience, a thorough knowledge of the necessary control tests and techniques, and the ability to recognize all reactions. .--.

The laboratory's inability to provide information concerning bloodstain evidence usually results from unsuitable specimens because of lack of timely submission or external contamination of the evidence.