`Sec. 3591. Sentence of death      

(b) A defendant who has been found guilty of--

            `(1) an offense referred to in section 408(c)(1) of the Controlled Substances Act (21 U.S.C. 848(c)(1)), committed as part of a continuing criminal enterprise offense under the conditions described in subsection (b) of that section which involved not less than twice the quantity of controlled substance described in subsection (b)(2)(A) or twice the gross receipts described in subsection (b)(2)(B); or

            `(2) an offense referred to in section 408(c)(1) of the Controlled Substances Act (21 U.S.C. 848(c)(1)), committed as part of a continuing criminal enterprise offense under that section, where the defendant is a principal administrator, organizer, or leader of such an enterprise, and the defendant, in order to obstruct the investigation or prosecution of the enterprise or an offense involved in the enterprise, attempts to kill or knowingly directs, advises, authorizes, or assists another to attempt to kill any public officer, juror, witness, or members of the family or household of such a person,

      shall be sentenced to death if, after consideration of the factors set forth in section 3592 in the course of a hearing held pursuant to section 3593, it is determined that imposition of a sentence of death is justified, except that no person may be sentenced to death who was less than 18 years of age at the time of the offense.