This just amazed me (see italicized text):
They [the FBI] say the core of their case will be the science, which produced the giant step from a globe of possible suspects to a single lab and a single flask.
Faced with the scientific mystery of the powder, government and outside scientists first looked at chemical isotopes in the attack strain for clues as to when and where the bacteria had been grown. Analyzing traces of the beef broth used to grow the anthrax, scientists measured carbon-14 left from nuclear weapons tests in the 1950s, whose quantity diminishes every year.
By calculating the ratio of carbon-14 to the normal kind in residue of plants eaten by the cow from which the broth was made, investigators learned by June 2002 that the anthrax had been grown within the last two years.
And on the falling cost of sequencing genomes of bacterium like Anthrax:
A second clue was developed from the new ability to sequence, or decode, the chemical letters of DNA. Scientists at the Institute for Genomic Research, a pioneer in genome sequencing, sequenced the full genome of the anthrax recovered from the blood of Robert Stevens, the first victim of the attacks...
Decoding the genome of a bacterium like anthrax may have cost around $500,000 in 2002, and even the F.B.I.’s budget would have been strained to decode thousands of genomes. A new generation of sequencing machines can now sequence bacterial genomes for around $500. But those machines did not become available until about 2005, which may have been another reason for the delay.