Is his travel patterns consistent with the locations the letters were mailed from?
If you are asking about Hatfill, his whereabouts during the day are provably the Frederick, Maryland area.
If you are asking about Al-Timimi, his whereabouts during the day are provably in the Falls Church, Virginia. FBI had tabs on his dinner on 9/16 and his lunch on 9/17 and had interviewed him the first week after 9/11. I do not believe he is suspected of being either the mailer or the processor. He is not believed to have the skill set for drying anthrax — he was a numbers guy, in a bioinformatics. I believe the FBI suspects him of accessing biochemistry information relating to concentration of anthrax using silica and passing it on.