Top forensic document investigators in the United States and overseas believe whoever sent the anthrax-laced letters in the United States may have delivered evidence that could help agents track down who's responsible.
Using a 25-year-old technique known as electrostatic detection, FBI investigators can recover handwriting impressions made on a piece of paper overlying the letters or envelopes, says Audrey Giles, a former Scotland Yard investigator who runs a document laboratory outside London.
"You might very luckily come up with an address, part of an address a telephone number, a note," says Giles
While there are no guarantees, the possibilities for this forensic technique hold promise, say experts.
"If people became careless, or if one of the letters came from a notepad, there's a good chance the FBI will find a clue that will lead them to the source," says Paul A. Osborn, a forensic document examiner in New Jersey who has seen copies of the letters.
The Electrostatic Detection Apparatus (ESDA) Giles demonstrated for ABCNEWS creates a small static charge over any impression left on a piece of paper. Tiny particles similar to photocopier toner are then sprinkled over a protective layer of film.
"In fact, the whole process is similar to what goes on in a photocopier," Giles point out.
In a matter of seconds these black particles are attracted to the charge, revealing traces of writing — just as a decoder pen reveals invisible ink.
The ESDA is highly sensitive, detecting impressions left as many as three or four pages down.
Osborn says there is a good chance at least one letter included with an anthrax sample was written on notepad, based on copies of letters provided him by media organizations.
Scanning for Clues
Video spectral equipment, which roughly resembles a desktop computer scanner, could be used to compare the ESDA results.
Using two handwriting samples she recovered with the ESDA, Giles scanned these into a Video Spectral Comparitor or "VSC 2000," to show how the FBI could enlarge and sharpen whatever handwriting their investigators might recover from the letters.
Spectral analysis also makes it possible to overlap several different samples to help compare the handwriting.
More advanced applications of the VSC uncover distinctions that could link different types of ink on the letters or the postmarks on the envelopes. Even blurred postmarks can be identified and matched using the spectral method.
If investigators eventually get ahold of a passport, they could use the VSC to determine whether the travel stamps are genuine.
As precise or advanced as some of this technology may be — Osborn and Giles say the FBI uses these methods and virtually the same equipment — Giles warns it's possible the forensic investigations might turn up nothing.
The postal system's sorting process may have left too many scuffs on the envelopes and letters to identify handwriting. If the letters and envelopes used were of a poor paper quality, impressions would be far more difficult to detect.
"Of course there might be nothing there at all, just random jottings," Giles says. "But it's all worth it when you're tracing an anonymous letter because there may be other evidence which you can compare."
In most cases, Giles says, any evidence gleaned from a document laboratory could be found within a few hours.
FBI spokesman Paul Bresson says one of the unusual challenges of dealing with the letters sent to Senate Majority Leader Tom Daschle and to media organizations in New York is the potential safety threat the evidence poses to investigators. Safety concerns have slowed the process somewhat.
"But it's fair to say the FBI will use every available method—from basic fingerprinting to DNA detection," Bresson says. "I'm sure some of the tests have been completed, but I doubt all have."
Osborn is certain one of those tests will be with the ESDA.
"They'd be damned fools if they didn't," Osborn says.