Chain of custody and DNA laboratory

Published: Last Edited:

This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.


In today's crime scene laboratories, the handling of all evidence is monitored closely, especially the DNA evidence. All DNA evidence must be handled in accordance to specific guidelines because of the use of the evidence in court room cases, and at no time should it be compromised. The DNA samples must be meaningful and legally acceptable. According to Butler (2005), "DNA techniques have become so sensitive that biological evidence too small to be easily seen with the naked eye can be used to link suspects to crime scenes." Every crime scene investigator, laboratory personnel and law enforcement agents need to protect the evidence regardless of the size or sample type from contamination, or from questionable doubt. Due to the specific standards for preserving DNA evidence, a high level of importance exists to maintain and use a chain of custody, especially in DNA handling, in an out of the laboratory.

Deoxyribonucleic Acid (DNA)

Deoxyribonucleic acid is the genetic material which makes up all living organisms. What is so unique about DNA, is that in humans, DNA is the same in every cell within the body (NIJ, 2003). In criminal investigations, DNA evidence is critical because each individual has unique DNA, except for identical twins, which can either link a suspect to a crime or eliminate them from the equation all together. Over the past decade, technological advances have been made which require smaller samples of DNA evidence as opposed to larger samples twenty years ago. This is why the chain of custody has been implemented to ensure proper collection, handling, preservation, transportation and storage of DNA evidence.

Types of DNA Samples

Just because DNA may not be seen in samples, it does not mean that there are none there. DNA can be obtained from; blood, fingernails, semen, saliva, hair, sweat, urine, feces, tissue, organs, brain cells, teeth, etc (NIJ, 2003). The slightest and smallest sample can convict a suspect if the DNA matches. Since the DNA is contained in the sample types and it must be extracted through technological procedures, preserving, storing and handling the samples requires precision and the protocols leave no margin for error.

Purpose of the Chain of Custody

The purpose of the documentation is to maintain the integrity of the chain of custody, especially if the evidence samples are DNA (DNAI, 2009). The chain of custody records the following: seizure, control, transfer, analysis, custody, and disposition of evidence. Evidence obtained refers to physical or electronic. The chain of custody is to establish that the evidence is directly from an alleged crime and it has not been fraudulently added. If a contamination occurred, it may be necessary to involve those who handled the samples, which is why the chain of custody is crucial in all samples of evidence. DNA samples can be obtained from the tiniest evidence, therefore, the chain of custody becomes a vital piece of information in a court of law. There is a lesser chance of contamination with fewer handlers and a shorter chain of custody. If by chance that there was a contamination, it can be traced to a specific point in the chain of custody.

Chain of Custody Standards

According to the Evidence Control Standards, for the Federal Bureau of Investigations (FBI), Standard 7.1.2 states (FBI, 2009):

"Chain of custody for all evidence shall be documented and maintained in hard or electronic format. The chain of custody shall include the signature, initials or electronic equivalent of each individual receiving or transferring the evidence, the corresponding date for each transfer, and the evidentiary item(s) transferred."

The chain of custody information which must be indicated on the forms or sample containers themselves is as follows, in no particular order (CPOLS, 2009):

  1. Name of collector
  2. Date, time, location of collection and description of condition that the sample was collected in.
  3. Description of sample collected
  4. Individual collected from
  5. Signature of the collector
  6. Signature of the individual who the sample was collected from or guardian/parent, if a minor

Many DNA testing companies abide by FBI standards, including Orchid Cellmark. Orchid Cellmark is a one of the worldwide DNA testing companies which has comprised strict procedures for the handling of DNA through a chain of custody. According to Orchid Cellmark, if the chain of custody is disrupted or questioned, the legality of the DNA could be dismissed in a court of law. Orchid Cellmark has implemented the following for the steps of DNA testing (Orchid, 2009):

  1. Identification of the tested party - involves verifying identities through government issued identifications and photographing the tested parties. Utilizes a consent form and a documented chain of custody form;
  2. Obtaining consent - is essential and can be obtained from an adult themselves or a legal guardian or parent for minors. Utilizes a consent form and a documented chain of custody form;
  3. Collection of specimens from the tested party - All collection samples must be collected by a third party to eliminate the possibilities of bias actions. All samples obtained are stored in the appropriate containers and labeled with the proper chain of custody information;
  4. Packaging of specimens - proper labeling and packaging of specimens
  5. Shipment of specimens - All parties which may handle the shipping of the specimen need to sign the date, time and their name on the package chain of custody form. In addition the tracking number or the shipment number now becomes part of the chain of custody form;
  6. Receipt of the specimens by the DNA laboratory - The name of receiver, date and time the package was received needs to be indicated on the chain of custody form. The specimens must also meet the requirements of the laboratory in order for the specimen sample to be accepted and signed for at the laboratory. Once the sample is accepted, the laboratory will usually assign a unique number or bar-code to that specimen;
  7. Transfer of specimen within the DNA laboratory - Each person who handles the specimen after receipt must indicate on the chain of custody form must indicate the date, time, and his/her signature and reason for using the sample. If a computerized bar-coded system is used, all of the apparatus being used will get a bar-coded sticker and scanned for every test or movement that the sample has been through;
  8. Storage of specimens - All storage of specimens will be documented in accordance to the accreditation standards and indicated on the chain of custody form. If a sample is removed from storage, again, the handler, date, time and reason for removal will be indicated on the chain of custody form (COPLS, 2009).

The chain of custody procedures are implemented as a protection method and also uphold the legality of the testing procedures and those executing the tests. Many companies throughout the United States test DNA on a daily basis and follow the standards set forth by the federal government to ensure the proper handling and credibility of the chain of custody.

DNA Laboratory Specific Procedures

In a laboratory, the chain of custody requires; where the evidence was kept, who had access, and who had possession of the evidence and when to be documented. The handling of the evidence is a consistent method of documentation. When evidence is transferred from one person to the next, the chain of custody will reflect all the pertinent information of the transfers. All personnel involved must complete the following chain of custody when transferring samples (CPOLS, 2009):

  • The name of the person from whom the evidence was obtained;
  • Date and time of possession of the evidence;
  • What protective steps were administered ensure that the evidence was not altered or contaminated;
  • If transferred again, the date and time of transfer and the name person receiving the transfer.

The level of importance in protecting evidence is extremely high, because evidence, in general, is fragile and the slightest failure in care could destroy the sample. Another reason for protecting evidence is because if the evidence is not in the same condition as it was when it was obtained, the credibility of the evidence diminishes and it could be dismissed from a court case.


The chain of custody is not only a form to provide a meaningful and legal piece of documentation, but it is an insurance policy to those who handled the specimen(s). Without the chain of custody, the integrity of the DNA evidence would be compromised, as well as those involved in the testing and handling of the evidence. The chain of custody eliminates the possibility of accusations of tampering, altering or any misconduct of evidence. In today's day and age, DNA is handled in scrupulously careful manner because only a minute sample is needed to either convict or eliminate a suspect in a crime. As tedious as keeping a chain of custody may seem, in the long run, protecting the evidence is the protection for the victim.


  • Butler, J.M. 2005. Forensic DNA Typing Biology, Technology and Genetics of STR Markers. 2nd. Ed. P. 34-35. Elsevier Academic Press, Burlington, MA.
  • (CPOLS) California Peace Officers Legal Sources. 2009. Section 2.8 Chain of Custody.
  • (DNAI) DNA Initiative. 2009. Chain of Custody.
  • (FBI) Federal Bureau of Investigation. 2001. Quality Assurance Standards for Forensic DNA Testing Laboratories. Volume 2. Number 3. Forensic Science Communications.
  • (NIJ) National Institute of Justice. 2003. What Every Law Enforcement Officer Should Know About DNA Evidence.
  • (OC) Orchid Cellmark. 2009. Chain of Custody. Overview.