Genetic testing

DNA samples from relatives helped confirm identity yesterday

By Bryan Bender and Carolyn Y. Johnson
Globe Staff / May 3, 2011

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Osama bin Laden’s identity was confirmed through a variety of techniques, including visual identification by Navy SEALs and by his youngest wife at the compound where he was killed in Pakistan, as well as photo analysis and genetic testing, according to a senior defense official who briefed reporters at the Pentagon yesterday.

The photo analysis, which relied on a computer technology that matched specific facial features, provided 95 percent certainty of a match. Yesterday morning, a test that compared the dead man’s DNA with samples collected from relatives, confirmed that the Al Qaeda leader had been killed, the official said on condition that he not be identified.

Genetic material taken from siblings and other close relatives can be used to confirm a person’s identity because people who are related share genetic material. Siblings, for example, share on average half of their genes.

Michael Rogers, a Michigan Republican who chairs the House Intelligence Committee, confirmed that DNA testing had taken place but refused to give details during a briefing at the US Capitol.

“I won’t give all the details of it . . . it wasn’t single-sourced, he’s got lots of places that his DNA could have been captured, through relatives or other means,’’ Rogers said. “One of the things that was important was to make sure that it was absolutely him. I think through the DNA testing and other things, it is clear beyond a shadow of a doubt that this was Osama bin Laden.’’

A television report Sunday night suggested that DNA used in the analysis was obtained from Massachusetts General Hospital, where a sister of bin Laden’s had supposedly been treated for cancer. But a hospital spokeswoman said yesterday she was unable to corroborate that report.

Massachusetts General Hospital said in a statement that its “policy is to not release patient information to law enforcement agencies without a subpoena or similar order, and that after a reasonable inquiry it could find no indication that it had received a subpoena regarding DNA for a relative of Osama bin Laden.’’

Other Boston hospitals declined to comment or said they had no record of supplying to authorities the DNA of a bin Laden relative.

Dr. Frederick Bieber, a medical geneticist at Brigham and Women’s Hospital with expertise in using DNA for identification, said that such analysis is commonly used, for example to identify people’s remains after mass disasters, such as Hurricane Katrina.

To do the testing, researchers extract DNA from a sample, then use a process called polymerase chain reaction to make many copies of specific sections of interest. Dyes are then added to allow comparisons of DNA fragments. Such work can be carried out rapidly — “in a hurry, overnight, in less than 24 hours,’’ Bieber said, in laboratories that exist in most developed countries.

Depending on the relationship between the individuals whose samples are being compared, scientists could take a variety of approaches to make an identification. They often look at “short tandem repeats’’ — stretches of DNA that vary in length among individuals but that are passed down and thus shared by close relatives. If the relative is a brother, scientists may look at areas of the Y chromosome, which only men have. If the sample comes from a sibling who had the same mother, scientists might look at mitochondrial DNA, which is passed on by mothers to their children. A mathematical technique known as a kinship analysis is used to assess the likelihood the genetic material comes from people who are related.

Senator Susan Collins of Maine, the top Republican on the Senate Homeland Security Committee, said she had been told that DNA testing was used in his identification, and she called the results “pretty conclusive.’’

“I, too, have absolutely no doubt that Osama bin Laden was killed yesterday, but I recognize that there will be those who will try to generate this myth that he’s alive, and that we missed him somehow,’’ she said. “In order to put that to rest, it may be necessary to release some of the pictures, or video, or the DNA test, to prevent that from happening.’’

Beth Daley and Theo Emery of the Globe staff contributed to this report. Bryan Bender can be reached at, Carolyn Y. Johnson at