Preservation and collection methods for biological evidence in DNA analysis

CRIMINAL JUSTICE FORENSICS & DNA: PRESERVATION OF BIOLOGICAL EVIDENCE

The objective of this work is to report on the methods and tools for investigation in the area of biological evidence as it pertains to preservation of biological evidence and specifically through review of five articles on this subject.

Biological evidence is defined as "evidence that is commonly recovered from crime scenes in the form of hair, tissue, bones, teeth, blood, or other bodily fluids." (West Virginia University: The Basics of Biological Evidence, 2009) It is reported that there may be only one form of biological evidence at the scene of a crime however; there also may be multiple forms of biological evidence present. (Ibid) It is critically important that the physical evidence at the scene of a crime be properly collected and preserved. (Ladd and Ladd, 2001)

Collection and Preservation of Biological Evidence

The work of Catalin, Andrei, and Mitrasca (nd) entitled: "Modern Methods of Collection and Preservation of Biological Evidence for Human Identification by DNA Analysis" states that physical evidence has become "increasingly important in criminal investigations...during the past few decades." Factors that affect the ability for obtaining a DNA profile:

(1) The sensitivity of PCR DNA typing methods is still limited;

(2) Sample degradation; and (3) Sample purity and DNA content of different types of samples. (Catalin, Andrei, and Mitrasca, nd)

Since all biological evidence is "subject to deterioration" it is critical that biological evidence be carefully collected and stored in order to ensure that the evidence is preserved in a condition that it is possible to obtain useful information from the analysis of the evidence. (Catalin, Andrei, and Mitrasca, nd, paraphrased)

II. Collection of Blood

Blood collection should be conducted by qualified medical personnel. Collection involves taking two tubes of blood, approximately 5 mL and collecting the blood in vacutainers with EDTA as an anticoagulant. Next, the tubes should be labeled with the date, time, name of the subject, location, name of the collector, case number and exhibit number. Blood samples are then to be refrigerated and should not be frozen. Blood samples should be submitted to the laboratory as quickly as possible. (Catalin, Andrei, and Mitrasca, nd, paraphrased)

III. Bloodstains

It is reported that objects that are small and that bear wet bloodstains "should be allowed to air dry and then collected as is." (Catalin, Andrei, and Mitrasca, nd) There should be efforts made for preservation of the "integrity of any bloodstain patterns during packaging and transportation." (Catalin, Andrei, and Mitrasca, nd) In the case of large objects in which it is not feasible to move them from the crime scene the web blood should be transferred onto a clean cotton cloth. It is important to label each object and container properly. (Catalin, Andrei, and Mitrasca, nd, paraphrased)

IV. Documentation of Semen Evidence

Semen evidence should be documented through use of "notes, photography, videotape and sketching." (Catalin, Andrei, and Mitrasca, nd) It is reported that one should use a "clean syringe or disposable pipette to transfer liquid semen to a clean, sterile test tube." (Catalin, Andrei, and Mitrasca, nd) The tubes should then be labeled with the "case and item number, date, time, location, and name of the collector." (Catalin, Andrei, and Mitrasca, nd) The specimen should be refrigerated and sent to the laboratory as quickly as possible. Liquid semen may be "transferred onto a clean cotton cloth by absorption. The cloth is then air dried, packaged, sealed and labeled properly." (Catalin, Andrei, and Mitrasca, nd)

VI. Most Common Applications of Blood Evidence

The work of George Schiro entitled: "Collection and Preservation of Blood Evidence from Crime Scenes" states that prior to the documentation and collection of blood evidence the value of the evidence must be recognized by the crime scene investigator and "how it fits in the overall events associated with the crime." (nd) Schiro states that the most common applications of blood evidence are those as follows:

(1) Finding blood with the victim's genetic markers (ABO blood type, DNA profile, etc.) on the suspect, on something in the suspect's possession, or something associated with the suspect (such as the suspect's fingerprints);

(2) Finding blood with the suspect's genetic markers on the victim, on something in the victim s possession, or something associated with the victim; and (3) Investigative information determined from blood spatter and/or blood location. (Schiro, nd)

VII. The Mobile Evidence Preservation System (MEPS)

It is reported by Forensics Solutions, Inc. In the work entitled: "The Mobile Evidence Preservation System (MEPS) that a new Mobile Evidence Preservation system (MEPS) provides the capacity to "properly and safely collect, store and preserve forensic evidence right at the crime scene." (Forensic Solutions, Inc., nd) This system allows for higher standards in the collection and preservation of evidence including the reduction of bacterial degradation "by provision separate cool/dry storage compartments for biological hair, fiber and trace evidence. Furthermore the HEPA filters are stated to "eliminate contamination from compartment to compartment, and item to item." (Forensic Solutions, Inc., nd) MEPS is stated to meet "OSHA and other state and federal health standards by immediately reducing staff exposure to blood-borne pathogens and infectious diseases." (Forensic Solutions, Inc., nd)

Summary & Conclusion

This work has related the importance of proper biological evidence collection and preservation. The importance of the proper performance of these criminal investigation tasks is not solely focused towards gaining convictions but as well the proper performance of these tasks may many times be the only thing standing between an individual who is innocent of a crime with which they have been charged and their wrongful conviction. The criminal investigator must be diligent in the collection and preservation of biological evidence in the area of forensics.