Modes of Identification: DNA
Nuclear DNA
In DNA identification, DNA profiles from individuals or from human remains are compared to reference DNA profiles obtained through personal items (eg, toothbrush), banked samples from the victim, and biological relatives. The number and reliability of identifications depends on the amount and quality of reference samples available. For many individuals, no reference profile is available, which limits the use of this mode of identification.
To obtain a DNA profile as part of biometric identification, a sample of skin cells is swabbed from the inside of the cheek, and sequenced by a specialized laboratory to create a DNA profile unique to the individual. This profile is then stored as a reference for later use if needed. The DNA swab is then destroyed – protecting the privacy of the individual.
The analysis generates a full DNA profile of the sixteen loci (specific locations on the gene) used and accepted for identification purposes across the world. These loci do not contain genetic information related to medical history or illness.
- DNA is not a stand-alone mode of human identification, but it can be used in tandem with other methods in a variety of disaster situations.
- DNA identification has several advantages (Pros)
- It is considered the gold standard for human identification in mass disaster and it can be used in almost any mass disaster situation
- The process of DNA identification using the 16 loci is standardized and well accepted, and standardization is international
- DNA is a highly accurate form of identification
- Biometric identification provides an archived DNA profile that can shorten response time for identification after a disaster. No samples will be retained – they will be destroyed once the profile is generated.
- In some cases involving substantial damage to the body, DNA may be the only viable method for identification.
- This method also has some limitations (Cons)
- Collection of usable DNA requires precise collection, expensive equipment, and a highly trained staff, which may not be available in remote or underdeveloped areas.
- Results of DNA analyses are not readily available for immediate response. It takes time to generate a profile and it must be interpreted by a trained analyst. Environmental conditions such as heat and moisture, and storage of samples may hasten degradation or limit the amount of usable DNA at the site of an incident.
- Personal items to use as a source of reference DNA may be unavailable or limited.
- In cases of mass casualty, DNA may be cross-contaminated among victims, making analysis difficult if not impossible.
- In the case of close relatives DNA identification may be less accurate. DNA identification also is not useful for differentiating between identical twins, because their DNA is identical.
- In the case of fire, heavy decomposition, or when just skeletal remains are available for identification, nuclear DNA cannot be used; however, mitochondrial DNA may be useful (see next section).
Mitochondrial DNA
Mitochondrial DNA (mtDNA) is a highly advanced method of genetic identification. Unlike nuclear DNA, which contains the genetic information both parents, mtDNA is an exact copy of the mother’s mtDNA. MtDNA is found in bone, teeth and hair – material that lacks nuclear DNA.
- This method is highly useful in certain situations (Pros)
- In some identification scenarios (particularly in cases of advanced decomposition or damage of the body by fire), mtDNA is the only tool available for genetic identification of remains.
- However, it also has limitations (Cons)
- MtDNA analysis is very costly.
