Federal Magistrate Carolyn Ostby ruled Wednesday that Tashala Hayman, 22, of Vaughn, is both dangerous and a flight risk and should not be released pending trial.
The package addressed to Kennedy was found last Thursday in the U.S. Capitol mail system and turned over to the FBI. Tests determined it contained soda bottles laced with cyanide, authorities said.
Authorities have said Hayman was preparing a similar package for mailing to Britain's Prince William at a Scotland address.
Federal marshals brought Hayman into the courtroom with a chain on her ankles and handcuffs attached to a chain around her waist.
U.S. Attorney Bill Mercer argued against allowing bail for Hayman, noting that she has lived in Montana only two months, has few if any ties to the state and faces serious charges involving threats to others.
Chief federal defender Tony Gallagher of Great Falls, Hayman's appointed lawyer, argued that she has no criminal record.
Drug agents in Washington last month informed the Cascade County sheriff's office that a Texas company had shipped two pounds of sodium cyanide to a Spokane, Washington, postal annex and a woman calling herself "Carolyn Smith." The package was forwarded to Vaughn and the fee to send it to Montana was paid with a check drawn on a bank account in Hayman's name, according to court documents.
Hayman was arrested on a state warrant for deceptive practices Aug. 8, after Great Falls police learned she had bought a pistol from a pawn shop with a stolen debit card number. Authorities said they later found Internet printouts of Social Security cards with different names and numbers in her purse, as well as a worker identification badge bearing her picture and the name "Carolyn Smith."
Mark Seyler, an FBI agent, testified at Hayman's detention hearing Wednesday that investigators who searched her trailer house in Vaughn also found immigration applications from Canada and Australia. The papers from Canada had been filled out, he said.
Seyler said investigators also found a package waiting for Hayman that contained a tranquilizer dart gun "designed to deliver chemicals into whoever was shot at."
The trailer house was virtually unfurnished except for a sleeping mat, he said.