Blood evidence collection and preservation in criminal investigations

¶ … Blood Evidence

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).

Collection

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).

Preservation

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 attached to the packaging. The procedure ensures the correct, orderly and responsible handling of evidence from the crime scene to the courtroom (NIJ, Bertino).

A receipt is issued to document the orderly transfer by a department's property and evidence section (NIJ, 2000; Bertino, 2013). This is usually done after a request for analysis and in a form, which lists the evidence items and a documented chain of custody. Every person or member of the chain who assumes custody from collection through analysis must sign the chain of custody document. This process is now automated through information management system bar codes. This chain neatly identifies every person who contributes to the analysis of evidentiary materials. When done, the evidence is either sent back to the submitting agency or stored at the lab. Again, the chain of custody will document and reflect this option. In addition, all relevant law enforcement reports, photographs, lab analyses, and other chain of custody documents are filed together and kept. They are made available to the prosecution but the defense may access them only if discovered. The chain of custody must be strictly preserved. When broken, the evidence carefully collected and kept may be ruled by the court as inadmissible. In order to safeguard the chain of custody, the number of persons handling the evidence should be limited. Their names, identification numbers, and dates of handling should be accurately listed on the chain of custody documents. Packaging should be properly sealed and marked before submitting. Signed or secure receipts should be obtained upon transfer of evidence to any department or section (NIJ, Bertino).