The story...

The FBI had DNA samples of 9-11 terrorists before the attack.
http://freedom4um.com/cgi-bin/readart.cgi?ArtNum=13219

Our take...

Although a fringe claim, this is still worth a look, if only to show how some "anomalies" can be created from almost nothing.

Let's begin with a clip of the original story.

Though the remains of 1,594 of the 2,749 WTC victims have so far been identified by name, Shaler makes clear the terrorists were a case apart.

To begin with, Shaler's office could not identify the three by name. That's because the 10 DNA profiles used to make the first matches were supplied by the FBI without names attached.

"No names, just a K code, which is how the FBI designates 'knowns,' or specimens it knows the origins of," Shaler wrote. "Of course, we had no direct knowledge of how the FBI obtained the terrorists' DNA."
http://www.nydailynews.com/front/story/354992p-302463c.html

This came from an article in the NY News on October 12th, and one thing you'll immediately notice is it doesn't say (or imply) anywhere that samples were obtained "before the attack". Please, go follow the above link just to confirm that. Done? Then you'll see the headline in the original story is simply an invention.

But how could they be obtained after the attack? In just the same way as the police do with any major crime scene, but there’s no need to speculate. Just do a little research: enter hijackers dna into Google and this BBC report pops up on the first page.

Forensic experts in New York say they have identified body parts of two of the 10 hijackers who flew planes into the World Trade Center on 11 September 2001.
Ellen Borakove, a spokeswoman for the New York Medical Examiner's Office, said the identifications had been made using DNA samples provided by the Federal Bureau of Investigation (FBI).

The FBI had collected the DNA from tiny traces of skin on the steering wheels of vehicles hired by the hijackers and from hair samples recovered from their hotel rooms.

Earlier this month, the FBI provided profiles of all 10 hijackers, including alleged ringleader Mohammad Atta, so their remains could be separated from those of victims.

"No names were attached to those profiles. We matched them, and we have matched two of those profiles to remains that we have," Ms Borakove said.

"We haven't finished our work, so it may be more," she added.
http://news.bbc.co.uk/1/hi/world/americas/2808599.stm

Can we say for sure this is true? Of course not. It does show the original story is less than complete, though, and there need not be anything suspicious in how the FBI derived their DNA profiles.