Quality control of evidence
Quality control of evidence (Forensic Science)
Quality-assurance programs have become commonplace in forensic organizations, and a number of accreditation bodies have been formed for the purpose of assessing the performance of forensic organizations against strict standards of practice. Accreditation allows organizations to demonstrate that they have been assessed and that their procedures were found to be satisfactory. They must also be able to demonstrate that those procedures are put into practice, however.
One of the most significant parts of any forensic organization’s quality-assurance, or accreditation, program is that relating to the handling of evidence. The organization must be able to demonstrate that each item of evidence has been handled appropriately from the moment of its discovery up to its presentation in court for trial, and sometimes through subsequent appeals and retrials. If it can be demonstrated that an evidential item has been, or may potentially have been, compromised or contaminated in some way, the significance of its evidential value becomes questionable. Doubt about the handling of a single piece of evidence may also call into question the evidential value of any items held or handled in any way by the same specific laboratory or individual. This may also have ramifications for other cases involving that laboratory or individual.
(The entire section is 203 words.)
Scene Security (Forensic Science)
When police personnel take control of a crime scene, they have a responsibility to take all reasonable steps to protect all potential evidence at the scene from deleterious change. Initially this involves ensuring that appropriate scene boundaries are put in place, a task that can be logistically difficult, particularly when a scene is outdoors.
After the scene parameters are in place, law-enforcement authorities must maintain control of the area to prevent entry to the scene by anyone other than those strictly required for processing and recording of the scene. Wherever possible, those individuals should all be well-trained, competent, and experienced crime scene personnel.
(The entire section is 103 words.)
Chain of Custody (Forensic Science)
When an item of potential evidence is identified, its location within the crime scene and its conditions must be recorded. This is typically done through photography, scene sketches, and general notes. After possession is taken of the item, it becomes part of an official exhibits register.
The exhibits register, or evidence log, is a list of all items that come into the possession of the police, whether collected from a scene or by other means, in relation to an investigation. The register typically assigns a unique identifier to each item and records a description of the item along with information concerning where it was found and by whom and when it was physically seized. After an item is entered into the exhibits register, the register records the physical location of the item and every instance when custody of the item changes.
During the course of an investigation, items may be transferred between sections of an organization or between organizations in order for required examinations to occur. Each section or organization should have its own process in place for recording the chain of custody of any items within its possession.
(The entire section is 189 words.)
The Importance of Packaging (Forensic Science)
The method of packaging of an item of evidence is also crucial to maintaining its evidential value. Inappropriate packaging may destroy evidence. For example, the DNA (deoxyribonucleic acid) in biological fluids can rapidly degrade if stored in a moist environment, such as inside a sealed plastic bag; such evidence should therefore be stored in breathable packaging, such as paper bags. Flammable liquid residues in a fire debris sample, in contrast, should not be packaged in paper, as this allows them to evaporate; such residues should be packaged in airtight containers. It is important that all personnel who handle evidential items understand how packaging can affect the items and thus potentially affect the results of subsequent analyses.
(The entire section is 116 words.)
Item Examination and Preservation of Item Integrity (Forensic Science)
During the laboratory examination of items of evidence—whether they are bullet fragments, bloodstains, or articles of clothing—some degree of physical handling of the items is inevitable. Following examination of an item, it is the responsibility of the examiner to be able to demonstrate that all reasonable steps were taken to ensure that the item was not detrimentally affected by the examination any more than was strictly necessary to perform the examination properly.
Crime laboratories often have strict requirements in place detailing what is considered to be acceptable practice in the examination of evidence. For example, the examination of items for DNA, particularly trace or contact DNA, can often involve elaborate precautions to prevent contamination. Examination spaces need to be thoroughly cleaned before and after items are examined. All equipment used must be either disposable or able to be cleaned thoroughly between item examinations. Examiners must wear disposable lab coats and gloves, face masks, and hair coverings to minimize their DNA contribution. This protective clothing must also be completely changed between the examinations of different items.
Records are kept of when an item was examined, who the examiner was, and where the examination took place. Any tests performed on an item are also recorded, as are the details of any subsamples collected....
(The entire section is 275 words.)
Further Reading (Forensic Science)
Adams, Thomas F., Alan G. Caddell, and Jeffrey L. Krutsinger. Crime Scene Investigation. 2d ed. Upper Saddle River, N.J.: Prentice Hall, 2004. Handbook for law-enforcement professionals focuses on excellence in the conduct of crime scene procedures, including the preservation of the integrity of evidence.
Inman, Keith, and Norah Rudin. Principles and Practice of Criminalistics: The Profession of Forensic Science. Boca Raton, Fla.: CRC Press, 2001. Provides an introduction to best practices in the forensic science profession. Includes discussion of evidence collection and preservation.
Pyrek, Kelly M. Forensic Science Under Siege: The Challenges of Forensic Laboratories and the Medico-Legal Investigation System. Burlington, Mass.: Elsevier Academic Press, 2007. Addresses the problems and challenges facing the field of forensic science, the history behind them, how they have been promulgated, and what could and should be done in the future to remedy them.
St. Clair, Jami J. Crime Laboratory Management. San Diego, Calif.: Academic Press, 2002. Presents excellent discussion of the unique needs and requirements involved in the management of forensic science laboratories.
(The entire section is 166 words.)