Pretrial Detention and Lifetime Supervision of Terrorists Act of 2003 - Amends the Federal criminal code to provide for pretrial detention for anyone who commits an act of terrorism transcending national boundaries (terrorist act) if the Attorney General certifies that the offense appears by its nature or context to be: (1) intended to intimidate or coerce a civilian population, influence the policy of a government by intimidation or coercion, or affect a government's conduct by mass destruction, assassination, or kidnaping; or (2) involved in or related to domestic or international terrorism.

Deletes a requirement that the commission of a terrorist act must have resulted in, or created a foreseeable risk of, death or serious bodily injury to another person in order to qualify for a period of supervised release of any term of years or life.