FBI Finds Unabomber Code -- Secret 9-Digit Number Appeared On Letters Predicting Bombings

WASHINGTON - Federal investigators say a secret identifying number used by the Unabomber was discovered in Ted Kaczynski's Montana cabin, adding a critical piece of evidence to the circumstantial case that they say links the reclusive mountain man to the Unabomber's crimes.

The nine-digit number, which was written like a Social Security number and was never revealed to the public before Kaczynski's arrest last month, appeared on correspondence in which the Unabomber predicted and then took credit for bombings. The number also appeared on a letter found in Kaczynski's cabin, federal officials said.

"He sent the number so we would always know that correspondence was from him," said one senior law-enforcement official. "He was concerned about copycats and persons claiming to be him.

Investigators hope that the identifying number and other new evidence will create conclusive links that justify charging Kaczynski with at least one of the fatal bombings claimed by the elusive figure once known only as the Unabomber. DNA analysis of saliva on stamps from Unabomber mailings has suggested correlations to Kaczynski's DNA profile, the "fingerprint" of genetic material unique to each human being, law-enforcement sources said.

Some officials believe the analysis is strong enough to link Kaczynski to a number of bombings and have initiated a final series of tests to determine the exact degree of probability that both samples came from the same person, said sources familiar with the case.

Investigators also found written material in Kaczynski's cabin about advertising executive Thomas Mosser, who was killed on Dec. 10, 1994, at his New Jersey home by a Unabomb package bomb, a source familiar with the case said. In addition, forensic experts have matched a typed label from a Unabomber package to one of three typewriters found in Kaczynski's home. Officials would not specify whether the label came from a package that contained a bomb or written materials mailed by the Unabomber. Forensic work is also centering on analyzing latent fingerprints found on Unabomb packages.

In the absence of a confession, witnesses or direct evidence that Kaczynski committed Unabomber crimes, the scientific detective work is likely to form the heart of any case brought against Kaczynski, the man suspected of engaging in an 18-year campaign of terror that left three people dead and 23 injured.

Federal investigators would have had to work quickly under speedy-trial provisions of federal procedure, but they unexpectedly find themselves with the time to slowly build such a case with every possible scientific tool. The reason: Public defenders representing Kaczynski have prolonged the pretrial period by filing motions claiming injury as a result of leaks to the media.

Kaczynski's Montana cabin proved a treasure trove of potentially damning evidence such as typewriters, a draft of the Unabomber manifesto, a letter to the New York Times, tools, bomb-design schematics, chemicals, a partially constructed bomb and a fully operational bomb, court documents and law-enforcement sources confirm.