DNA Identification in Mass Fatality Incidents
Robert Shaler
One of the important decisions that must be made within the first 48 hours of a mass disaster event concerns the establishment of family assistance centers. This is extremely important, because the manner in which personal effects and kin samples are collected affects the efficacy of the entire identification effort.
After considering the role that DNA will play in an identification effort, the type(s) of DNA analysis needed, and the duration of the recovery effort, the laboratory must determine the analytical processes. Ultimately, it must be decided whether a laboratory has sufficient capability and capacity to do the work. To assess this, several key variables—described in exhibit 3—should be considered.
Exhibit 4, an Estimated DNA Analysis Workload Worksheet, can be used to help predict the labor and material resources required for the DNA analysis.
Currently, most forensic DNA laboratories are proficient in STR analysis, proven to be a powerful tool in many mass fatality incidents since the 1990s. For example, DNA identifications in three airline disasters—Swiss International Air Lines flight 111 (September 2, 1998), Alaska Airlines flight 261 (January 31, 2000), and American Airlines flight 587 (November 12, 2001)—were made exclusively with STRs; no other technologies were needed to identify every victim.
STRs are particularly informative on well-preserved soft tissue and bone samples. Analysis of the compromised remains after the WTC attacks demonstrated that STRs also work with degraded tissue and bone fragments if the DNA extraction process is optimized. However, STRs alone are often not sufficient for identification when samples are severely compromised. In those situations, additional methods—such as mtDNA sequencing or Single Nucleotide Polymorphisms (SNP)—are likely to be necessary to generate sufficient genetic markers to reach a statistical threshold.
The DNA identification response to a mass fatality incident demands forensic casework skills and high throughput genotyping or databasing, whether from the public and/or private sectors. Because there are differences between STR genotyping for medical or research purposes, laboratories that can perform high-quality clinical or research STR genotyping should be used only after careful consideration.
DNA from human remains in a mass fatality incident—and personal reference sample items—are collected from many different sources, each requiring chain-of-custody protocols not typically used by clinical or research laboratories. To increase the probability of obtaining full profiles from the personal effects samples, DNA should be extracted using forensic casework extraction protocols. Likewise, full polymerase chain reaction (PCR) volumes usually are necessary to develop complete profiles from the victim samples.
On the other hand, kinship samples are more uniform and lend themselves to standardized high throughput processes that are used (although perhaps with different protocols) by forensic databasing laboratories and some nonforensic genotyping laboratories. Forensic databasing laboratories often have sophisticated information technologies for tracking samples and avoiding mixups. In addition, forensic databasing laboratories often are more experienced than forensic casework laboratories with outsourcing work to private laboratories.
Depending on the mass fatality event, kinship samples, for example, might be analyzed by high throughput clinical laboratories that are willing to implement appropriate protocols (assuming that the kin are those of the victims, not kin of those suspected of being perpetrators of the mass disaster). This procedure focuses the most rigorous forensic protocols on the limited and compromised victim samples. And, although mass fatalities from natural disasters may fall outside the parameters of a forensic investigation, laboratory directors and MEs should weigh all potential issues before departing from chain-of-custody and other forensic procedures.
However, most mass fatality events likely will require a forensic approach for at least some of the samples. In these instances, as previously noted, laboratories that can perform high-quality clinical or research STR genotyping will have to modify their protocols and analysis methods. For example, clinical and research laboratories may not typically use the same (or any) molecular ladders as size standards for allelic interpretation. It is important to ensure that all laboratories involved in the DNA analyses use protocols that permit standardized evaluations of victim profiles. Standard STR forensic DNA marker analysis is based on well-established and comprehensive procedures that enable profile frequencies to be calculated from existing and well-validated databases.
Culture and practices can vary among forensic and nonforensic laboratories. If they are not addressed at the beginning of a mass fatality DNA identification effort, these differences can lead to communication problems. A laboratory director also should keep in mind that some terms—“acceptable molecular ladder,” “acceptable positive and negative controls,” and “standard reaction volume,” for example—may need to be fully defined when a nonforensic vendor laboratory is used.
In addition to the actual DNA analysis, the laboratory may also be responsible for some of the following activities:
- Sample accessioning and tracking.
- Making identifications and resolving metadata problems.
- Quality control.
- Interacting with families and the media.
- Long-term sample storage.
If these activities are overlooked during the development of a mass fatality plan, resource shortfalls likely will occur.
Generally, after a DNA profile is generated, it should take about the same time to evaluate the data for an identification as it takes in a paternity/biological relationship case analysis. [Note: Although more than a quarter of a million parentage tests are performed annually in the United States, biological relationship testing, such as paternity analysis, is rarely performed in forensic laboratories. Because many of the laboratories that perform such tests use some of the same STR loci that are used by U.S. crime laboratories, it may be prudent to consult with experts in parentage testing when preparing a mass fatality response plan. The American Association of Blood Banks is responsible for accrediting the Nation’s parentage-testing laboratories.]
The laboratory director must consider the impact of a mass fatality incident response on the laboratory’s primary mission. Capacity issues must be addressed in the context of routine, crime scene casework or, in the case of a databasing laboratory, convicted offender analyses. As resources are redirected to a mass fatality identification effort, backlog and turnaround times are likely to increase for regular casework. Even though local police and officers of the court may support the laboratory’s role in the mass fatality incident response, they may still expect their cases to be completed in a timely manner. Plans for managing both a mass fatality incident response and routine casework should be developed before the need arises.
The duration of the recovery effort also has major implications for a laboratory’s capacity. A rapid recovery effort (1 to 3 months) creates a spike in the laboratory’s workload; however, because of the short duration of such a response, the laboratory may be able to quickly recover. Also, local law enforcement professionals and officers of the courts may be more tolerant of delays if they occur for only a short period of time.
With respect to more lengthy recovery efforts, the arrival of samples may be uneven, and the laboratory may be able to absorb the additional workload without affecting turnaround time on routine casework. However, a prolonged DNA identification effort may drain people and resources—and good planning can help mitigate disruption if a laboratory receives a large number of samples over an extended period of time.
