In a possible break for the FBI's investigation of the anthrax letters of 2001, scientists have discovered that the mailed anthrax was a mix of two slightly different samples, giving the bacteria a distinct signature that might make it easier to match with a source, according to two non-government experts who have been told of the finding.
The discovery that bacteria taken from the letters all grew in the double pattern was made at least a year ago, and it is not known whether the FBI's hunt for a matching sample has succeeded. The bureau and its scientific consultants are screening dozens of anthrax samples collected all over the United States and in some foreign countries, seeking the closest match to the spores used in the attack, according to a scientist who advises the FBI.
The revelation of the double pattern of the mailed anthrax comes as the FBI is due Tuesday to give a Washington judge a secret progress report on the investigation the bureau calls Amerithrax, which is well into its third year without visible results.
The FBI progress report, requested in March by U.S. District Judge Reggie B. Walton, is likely to be less about old-fashioned police work than newfangled science, according to statements made in court by FBI and Justice Department officials. The case of the anthrax-laced letters that killed five people and sickened at least 17 others in 2001 has become the first major test of an emerging scientific discipline called bioforensics, the use of genetic analysis and other modern laboratory tools to track germs used in an attack back to their origin.
FBI spokeswoman Debra Weierman declined last week to discuss the investigation, except to say that tests on the anthrax powder have not been completed. But experts on the fast-developing science of biological sleuthing say it should by now have helped the bureau to substantially narrow the search.
"I think we have the science now to trace the anthrax to a particular lab," said Babetta L. Marrone, a cell biologist at the Los Alamos National Laboratories and a member of an FBI advisory group on bioforensics.
Still, she says, finding the source lab will not by itself identify a perpetrator, only reduce the number of potential suspects. "If I had to guess, I'd say what has the FBI stumped is the non-scientific stuff," Marrone said.
Walton is presiding over a lawsuit filed by former Army biowarfare expert Dr. Steven J. Hatfill, who says the government wrecked his career and upended his life with a deliberate campaign of leaks falsely suggesting that he was the anthrax mailer. Hatfill's lawyers want to obtain FBI documents and question government officials to support his claims.
In successfully seeking to put on hold Hatfill's lawsuit and another filed by the widow of a Florida anthrax victim, the FBI claimed in court early this year that the investigation was at a "critical stage" and that the litigation could endanger investigators' work.
An affidavit filed by FBI Inspector Richard L. Lambert in January described a major scientific effort to define the "specific forensic signature" of the attack anthrax.
"To forensically characterize the anthrax evidence ... the FBI has contracted with 19 government, commercial and university laboratories which are performing research, analyses and evaluations to assist the FBI Laboratory," Lambert wrote. "Most of these scientific initiatives are scheduled to be completed within the next six months. If successful, these initiatives will ... facilitate the attribution of the anthrax used in the attacks to one or more U.S. and foreign laboratories."
Of 30 FBI special agents and 13 U.S. postal inspectors working full-time on the case, officials say, eight of the FBI agents have a doctorate "in a scientific discipline related to the investigation."
"I've been impressed with the patience and perseverance of our partners in the FBI," said Claire M. Fraser, director of the Institute for Genomic Research in Rockville, a private organization that is carrying out much of the genetic analysis for the bureau.
Fraser said she could not discuss specific findings related to the investigation. But she said that after initial skepticism, she has been pleasantly surprised by the progress made in the past year in finding forensically useful ways to distinguish samples of anthrax from one another.
Still, she said genetic analysis of samples of pathogens is not nearly as advanced as the human DNA testing that has become routine in investigations of murder, rape and other crimes. "We're not even close to being at that level," she said.
Ronald Kessler, a Washington author who has written several books on the FBI, said the Amerithrax investigation represents the largest mobilization of inside and outside scientists in the bureau's history.