During an interview with The New York Times, attorney Sabrina Shroff said she plans to request a hearing to determine whether her client freely waived his right to have a lawyer present while being questioned during the first 12 days he was in custody after his Sept. 29 arrest.
Mansour Arbabsiar, a Corpus Christi, Texas, used-car salesman, allegedly cooperated with investigators, confessing to the assassination plot and providing key information linking Iran to the plan.
"There has to be a deep concern about the voluntariness of consent to that long a period of detention," Shroff told the Times.
The newspaper said controversy over Arbabsiar's cooperation with authorities highlights legal and political problems raised when the criminal justice system handles terrorism cases.
Shroff wants a hearing to determine whether her client's "consent was freely given, or whether it was unlawfully extracted."
U.S. Attorney General Eric Holder said elements of the government of Iran were behind a conspiracy to hire assassins from a Mexican drug cartel for $1.5 million to kill Saudi diplomat Adel al-Jubeir.
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