Suspect's brother agonised over Unabomber

David Kaczynski agonised for more than six months before alerting the FBI to his suspicions that his brother, Theodore, arrested last Wednesday in Montana on charges of possessing explosives, might be the notorious Unabomber whose letter-bombs have killed three people and injured 23 across America over the past 18 years.

Tony Bisceglie, the Kaczynski family lawyer, said yesterday that David Kaczynski first began to suspect his brother last summer after reading accounts of the locations where the bombs had been mailed. In September, however, his fears were amplified with the publication in the New York Times and the Washington Post of a manifesto by the Unabomber. "David Kaczynski read the manifesto with the idea that he would be able to immediately discount any connection between his brother and the Unabomber," Mr Bisceglie said. "Unfortunately, when he read the manifesto, he was unable to do that."

In October, driven by a "very sincere desire to ensure that no further lives were lost", David Kaczynski gathered samples of his brother's writings and consulted experts who "concluded that there was a significant probability that that the manifesto and these writings were written by the same individual," Mr Bisceglie said. He added that David had gone through "a great deal of anguish" before deciding to report his brother. "This is a very loving family."

The FBI was said yesterday to be accumulating evidence to upgrade the charge against Theodore Kaczynski from possession of explosives to murder.