A dust mask found in a suspect's trash may link him to an apparent attempt to poison U.S. President Barack Obama and other public officials.
James Everett Dutschke is accused of sending a toxin called ricin through the mail.
According to an affidavit unsealed yesterday, the dust mask tested positive for ricin.
And a witness said Dutschke talked years ago about putting "a poison" in envelopes.
Dutschke has denied any involvement.
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