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How DNA may have confirmed bin Laden’s death

DNA.Violet.jpgThe US government has said that DNA samples from family members of Osama bin Laden were used to positively identify his body with “99.9 percent” certainty. How would this work, and how can the government be so certain?

Modern forensic techniques analyze short tandem repeats — pieces of DNA that are copied different numbers of times in different individuals on the chromosomes that contain an individual’s genetic code. Christie Wilcox blogs about how polymerase chain reaction and genetic sequencing are used to count the number of tandem repeats in a genome. It’s then easy to compare the tandem repeat profile between two individuals to find out whether their DNA profiles match.

Chad Nusbaum of the Broad Institute of MIT and Harvard in Cambridge, Mass., estimates that this process would take five or six hours, or even faster in a lab using proprietary technology dedicated to forensic identification. This would have given military analysts time to perform a DNA analysis after the U.S. raid on Monday morning in Pakistan, and deliver results to President Obama by the time of his announcement on Sunday night in Washington, DC.

The equipment necessary for such a DNA analysis could have been located on a ship or at a base near the site of the raid, for instance, at Bagram Airfield in Afghanistan.

But how can the government be so certain that the man it has killed is bin Laden?

The strongest possible match would be made by comparing a sample taken from the putative bin Laden body to previously collected samples of his own DNA.

“My guess is maybe they had samples of bin Laden’s that could have been around for a while,” says Robert Shaler, who directed the DNA identification efforts for victims of the September 11, 2001 terrorist attacks on the World Trade Center in New York City. Shaler points out that his team was provided with DNA profiles of some of the hijackers involved in the 9/11 attacks to identify their remains in the World Trade Center rubble, and that a sample of bin Laden’s own DNA could have been collected by military or intelligence agents from places that bin Laden had lived or visited.

Samples also could have been collected from any of bin Laden’s living siblings or children, either with or without their knowledge, by obtaining discarded material bearing their DNA, such as beverage cups or dental floss, says David Kaye, a lawyer at Pennsylvania State University.

Bin Laden reportedly has no full siblings, as he was the only child born to his mother and father. However, his mother remarried after she and bin Laden’s father divorced, so bin Laden reportedly has three half-brothers and one half-sister born to her, as well as dozens of half-brothers and half-sisters also born to his father. He also is said to have fathered as many as 26 children.

“Bin Laden’s relatives might have cooperated, or even if they didn’t, agencies might have obtained DNA samples surreptitiously — it’s a well known practice in law enforcement now,” says Kaye, who last year published a book, The Double Helix and the Law of Evidence, on genetic forensic evidence in the criminal justice system.

For instance, DNA collected from a discarded slice of pizza was used to identify the man charged last year with the so-called “Grim Sleeper” murders in California. DNA taken from the alleged killer’s son was also used in that case.

The strength of a match made between bin Laden’s putative DNA and that of his relatives would depend on how many related DNA samples are available for comparison, and how closely they are related to bin Laden, says Allison Williams Dobson, a lawyer and molecular biologist who works with the Center for Genomics and Society at the University of North Carolina Chapel Hill.

“The more siblings and children you have samples from, the easier and more certain it would be,” Williams Dobson says.

It is likely that sequencing of DNA from mitochondria — organelles in the cell that are passed down from mother to child — could have been used to confirm that the man killed in Afghanistan was a sibling to bin Laden’s half-sisters and brothers, or was the son of bin Laden’s mother, who is still living. Since mitochondria are passed down from mother to child, they can establish with near certainty that two individuals are siblings, says Mary-Claire King of the University of Washington, who pioneered the use of mitochondrial DNA to identify victims of mass killings and homicides in the 1990s.

“Mitochondrial DNA sequencing would be the most certain way, by far, of identifying two people as full siblings,” King said.

Short tandem repeat analysis could also be conducted on the y-chromosome, which is passed down from father to son. Such an analysis could be used to link the putative bin Laden to any of his known half-brothers or sons, further strengthening the evidence that it was indeed he who was killed in the Navy raid in Pakistan.

If it is true that bin Laden was the only son born to his mother and father, a combination of y chromosome and mitochondrial DNA markers could yield a strong match to bin Laden himself, because none of his half-brothers would have inherited the same combination of y chromosome and mitochondrial DNA markers that he has.

Short tandem repeat analysis could also have been conducted on nuclear chromosomal DNA from many bin Laden siblings and children, further cementing the case that the killed man is Osama bin Laden himself.

“If they have the right samples, the identification is virtually certain,” Shaler says.

In addition, news reports have also mentioned other identification techniques, such as facial analysis, that would complement the DNA analysis.

Whatever DNA evidence does exist, Williams Dobson points out, the U.S. government must feel very confident about it.

“They must be quite sure it is him, because if they are wrong, we will have a video from him circulating pretty soon, showing that he is actually alive,” she says.


  1. Report this comment

    Charles Stone said:

    Why was his body buried so quickly in the ocean where it an not be recovered? Where are the photos of his corpse esp the face and those of his son and wife? There is some ecvidence that he was killed in Tora Bora in 2001. That is widely believed in Pakistan. Where is his kidbey dialysis machine? Your comments are appreciated. Charles W. Stone

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    Greg Hampikian, Ph.D. said:

    Mitochondrial DNA would not be the most certain method for ID. Coincidental “matches” to mitochondrial DNA are very common. In fact, it is best not to use the term “match” with mitochondrial DNA; people identified as dead by such techniques, have suddenly shown up very much alive. Exclusion statistics for mitochondrial identification are often in the range of only 1 in 2,500—hardly a match.

    —Greg Hampikian, Ph.D. Boise State University, Biology, and Criminal Justice.

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    Robert Kaus said:

    Greg, you aren’t using very good analytical thought here. It isn’t as if they killed some random person who “just happened” to have mitochondria matching bin Laden. Combine the corroborating intelligence that bin Laden lived in the compound and it becomes VERY likely to be a match.

  4. Report this comment

    Carlos Chau said:

    So glad to see this post. I was thinking exactly on how the calculation & experiment were done

  5. Report this comment

    pavlos pavlidis said:

    I think it’s right-handed 🙂

  6. Report this comment

    Shamsu haq said:

    If Us goverment is using so many techniques for the identification of body of Bin Laden, why they could not preserve his body atleast for 2 days? Why were they so quick to throw his body in the ocean? Is not it likely that , Bin Laden was dead naturally some years before,bt now Us govrnment is confirmed about his natuaral death and use the sitiuation in their fever such that they killed anyone ramdomly by preplaning and try to make the cover story such that Dna fingerprinting could be used for confirmation?? There is no guarantee how much this testing would be fair? Its just the conspiracy like that of 9/11..this is wouthout any doubt.

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    Tao Liu, M.D. said:

    I want to say that science is power.

  8. Report this comment

    Josh Saldivar said:

    The DNA shown in the figure is right-handed.

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    Misterio Vida said:

    theoritically speaking, mitochondrial DNA should be the same for all individuals having the same maternal lineage except mutations… so osama or his brother will be having the same mitochondrial DNA… it is used only in ancestry and in cases where analysis with normal DNA is not possible because of high degradation for example in the case of mass disaster or ancient graves…

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    ashu kumar jha said:

    i am B.Sc biotech&Ms.c forensic scence studant so may project wark DNA fingerprint. laden death conform the DNA test mitocondrial dna test RFLP marker are used then sequenceing gene matchin family mamber.

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    Larry said:

    First, an exact mitochondrial DNA match can extend back to a common matriarch thousands of years ago, so it is practically meaningless for identification.

    But more importantly, this entire article is pure speculation based on a bald assertion with no evidence whatsoever. What is needed is independent international verification—e.g., by Russian and Chinese labs. Even then, identification of bin Laden’s DNA only proves that the United States has that DNA, not that the US necessarily has or had bin Laden himself. Any sensible court would additionally require sworn testimony—under cross-examination—of the DNA’s provenance.

    Indeed, all independent evidence suggests that Osama bin Laden died in December 2001, probably from kidney failure (and lack of functioning dialysis machines in Tora Bora).

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    Muhammad Israr said:

    irrespective of who the osama was, in scientific terms, they should have taken more samples and there was no need of such a hurry, i very much doubt if an independent court and jury will accept such an evidence…

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