H.R.1914: To amend title 18, United States Code, to ensure the death penalty for terrorists, and for other purposes.

Terrorist Death Penalty Act of 2007 - Amends the federal criminal code to: (1) impose the death penalty for certain terrorist offenses; (2) include as death penalty aggravating factors whether the defendant committed an offense after substantial planning or engaged in conduct resulting in the death of another person in order to obstruct the investigation or prosecution of any offense; (3) permit the impaneling of a new jury when a unanimous death penalty recommendation cannot be reached; and (4) expand the power of a court to impanel a jury of less than 12 members in a death penalty proceeding.

Amends the Federal Rules of Criminal Procedure to increase the number of allowable alternate jurors from six to nine and permit four additional peremptory challenges when seven, eight, or nine alternative jurors are impaneled.