By Ben Butkus
Three days after President Barack Obama announced that US Special Forces had killed Osama Bin Laden, government officials have yet to disclose details on the DNA testing that resulted in a "99.9 percent" identity match, and it remains unclear whether they will choose to at all.
Yet the rapid DNA test results, combined with facial recognition techniques, verbal identification by one of Bin Laden's wives, and other evidence played an integral role in proving that the body was indeed his.
In a press briefing early Monday morning, US officials said that the initial helicopter raid on Bin Laden's compound in Abbottabad occurred in the "early afternoon" Eastern Standard Time on Sunday. On Monday afternoon, John Brennan, assistant to the president for homeland security and counterterrorism, said that the "99.9 percent confidence" statistic was primarily based on DNA test results.
A spokesperson for the Central Intelligence Agency this week told PCR Insider that DNA testing of Bin Laden was likely performed by some combination of US military and CIA personnel, but he declined to provide additional details, saying that government officials were still weighing the proper course of action for releasing evidence surrounding Bin Laden's death.
Nevertheless, forensics experts have almost unanimously stepped forward to support the idea that the DNA testing – most likely Y-linked short tandem repeat PCR amplification and analysis – could easily have been performed in the amount of time and location it is purported to have been, using industry-standard products.
"All PCR-based systems are pretty fast," Jenifer Smith, a former high-level forensics official at the CIA and Federal Bureau of Investigation, told PCR Insider this week. "What tends to slow labs down, and why they can't do it in the blink of an eye, is other caseload issues. If you need a DNA profile … relatively quickly, within hours … you can get one using standard testing already available."
According to Smith, currently a professor of forensic science at Pennsylvania State University, this is especially true considering that the operatives who killed Bin Laden likely had access to large, uncontaminated quantities of DNA from his corpse.
"The hard part in DNA [testing] now would be mixtures [of DNA], or very degraded samples," Smith said. "Given that … they were probably able to get a good sample from him, and that the quality of the DNA would be great … they wouldn't have [had] to use any special testing [other] than what's already available to law enforcement all over the country."
It turns out that there are not many commercial options currently available to law enforcement agencies in the US or elsewhere. Although its exact market share is unknown, Life Technologies' Applied Biosystems business undoubtedly owns the largest piece of the forensic DNA testing pie, and its products were likely used in some aspect of Bin Laden's DNA testing, company officials said this week.
Indeed, the FBI on more than one occasion has endorsed the use of various forensic kits in Life Tech's AmpFℓSTR product line (PCR Insider, 1/28/2010 and 5/20/2010); although it is unknown whether Life Tech has forensics contracts in place with the FBI, CIA, or US military.
Leonard Klevan, president of human identification at Life Tech, told PCR Insider that although he "can't really discuss specific customers, I would say we're the world leader" in forensic DNA testing. Lisa Schade, director of global marketing for Life Tech, added that the company's products in this area are "an international standard" and are the "most trusted for human identification worldwide."
Life Tech's other major competitors on this front include Promega and Qiagen, Klevan said, although Schade claimed that these firms compete "along different portions of the workflow," such as DNA extraction and purification, thermal cycling, or analysis, "but not across the entire workflow."
Smith declined to speculate on the specific DNA testing products that might have been used by the CIA or FBI, but agreed that they would likely be "one of the two main forensic kits out there" from Applied Biosystems or Promega.
"The best bet is to go with what has already been tested and used in the courts," Smith said. "The reliability of these kits has already been validated and proven. They're not going to use methods that haven't been validated in the hands of other organizations, because now is not the time to go too novel. And there really is no need, in this case, I'm guessing, because of the sufficiency of the sample they're getting."
Smith added that if the operatives had obtained a "highly mixed sample, or a low-level sample, then maybe they'd have to use some non-standard techniques. But if you're basically given a blood sample from a person, there are sufficient testing methods available that could be used. Whether they were used in this case … they may or may not choose to tell us."
Klevan said that Life Tech's most frequently used kit, for "situations where you have plenty of DNA," is the AmpFℓSTR Identifiler Plus. The company also offers the AmpFℓSTR MiniFiler kit for more degraded DNA samples; and various kits for specific types of studies such as autosomal STR, Y-STR, and mitochondrial DNA analyses. Meantime, Promega offers several kits under the brand name PowerPlex for similar types of analyses.
According to Klevan and Schade, a typical workflow in a case such as Bin Laden's would most likely involve a direct blood sample deposited onto an industry-standard Whatman FTA card or directly into a sampling tube, from which DNA can be quickly and easily extracted, and purified if necessary, using any number of commercial kits.
"You would then do your amplification using one of the kits identified as a global standard," Klevan said. "And then you would run that on a capillary electrophoresis system," of which Life Tech offers several. Lastly, a technician would use software such as Applied Biosystems' GeneMapper ID-X to compare alleles from Bin Laden's DNA to that of a reference sample.
Klevan echoed Smith's assessment that such a process could be completed rather quickly if it were the sole focus of attention.
"If it's a very high-priority case, even using standard operating procedures, using our workflow, you could turn around a standard analysis in half a day," Klevan said. "If you don't do anything else, and you're completely focused on that case, and you're doing extraction, amplification, and detection — it's really the analysis that takes the longest, depending on what you're comparing it to.
"My guess, and I don't know for sure, is that they probably had set up logistics to move the sample to a laboratory in the vicinity," Klevan added. "It would then probably take six hours to get a complete identification and proceed with what they did."
Regarding the remoteness of the location, Smith also believed that it wouldn't be difficult for US officials to conduct the testing in a fairly rudimentary or temporary lab in the general vicinity of Abbottabad.
"Since they had opportunity, it sounds like, to plan for what was going to happen, I'm sure that was worked into the planning — getting the samples to the right people," Smith said. "If they have facilities overseas, that would have shortened the timing. A lot of these tests can be done in the field — and I'm not talking about a table in the middle of a desert — but if there are actual well-equipped labs over there where they're doing DNA typing, those could have been used."
One remaining unknown is that of the reference sample against which Bin Laden's DNA was compared. While initial media reports stated that the reference sample was obtained from Bin Laden's sister several years ago when she was being treated for brain cancer at Massachusetts General Hospital, that story was denied by MGH officials. The White House has not yet provided details on the reference sample.
"They'd have to have a reference sample ready to go," Smith said. "Either from him; or a composite one put together from relatives. They wouldn't have been able to make a match quickly if they didn't have some kind of a reference sample."
Klevan pointed out that a composite reference constructed from the DNA of various family members would complicate analysis and delay a positive ID, but that it was still possible.
"If somehow they had a sample from him, that's much easier – that's simply, 'Do these two samples match?' Klevan said. In that case, officials would conduct autosomal STR analysis instead of Y-STR analysis.
"If they have samples from his family, then it becomes a more complicated analysis, but there are still people that can do that pretty quickly," Klevan said. He also speculated that the "99.9 percent" statistic provided by US officials may have provided a small hint regarding the reference sample.
"Being that it was 99.9 percent … makes me think it was … a family relationship," he said. "Because if it were from him, it would just be a match."
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