18 USC 1121
Murder of a state or local law enforcement officer or other person aiding in a federal investigation; murder of a state correctional officer
TITLE 18 - CRIMES AND CRIMINAL PROCEDURE
PART I - CRIMES
CHAPTER 51 - HOMICIDE
Sec. 1121. Killing persons aiding Federal investigations or State correctional officers
(a) Whoever intentionally kills -
(1) a State or local official, law enforcement officer, or other officer or employee while working with Federal law enforcement officials in furtherance of a Federal criminal investigation -
(A) while the victim is engaged in the performance of official duties;
(B) because of the performance of the victim's official duties; or
(C) because of the victim's status as a public servant; or
(2) any person assisting a Federal criminal investigation, while that assistance is being rendered and because of it, shall be sentenced according to the terms of section 1111, including by sentence of death or by imprisonment for life.
(b)(1) Whoever, in a circumstance described in paragraph (3) of this subsection, while incarcerated, intentionally kills any State correctional officer engaged in, or on account of the performance of such officer's official duties, shall be sentenced to a term of imprisonment which shall not be less than 20 years, and may be sentenced to life imprisonment or death.
(2) As used in this section, the term, "State correctional officer" includes any officer or employee of any prison, jail, or other detention facility, operated by, or under contract to, either a State or local governmental agency, whose job responsibilities include providing for the custody of incarcerated individuals.
(3) The circumstance referred to in paragraph (1) is that -
(A) the correctional officer is engaged in transporting the incarcerated person interstate; or
(B) the incarcerated person is incarcerated pursuant to a conviction for an offense against the United States.
(c) For the purposes of this section, the term "State" means a State of the United States, the District of Columbia, and any commonwealth, territory, or possession of the United States.
Source: Office of the Law Revision Counsel, US House of Representatives, "Search the United States Code," www.uscode.house.gov (accessed Sep. 6, 2012)