They did not contain anything nuclear, biological or chemical, but the homemade explosives allegedly used by accused Boston bomber Dzhokhar Tsarnaev and his brother Tamerlan were still weapons of mass destruction (WMDs), as far as the federal government is concerned.

In filing charges against Dzhokhar Tsarnaev, the U.S. Department of Justice accused him of using WMDs during the marathon and against police during the shootout in Watertown.

Michael Crowley at Time explains that federal law defines WMDs “in extremely broad terms. The relevant statutes define almost any significant explosive device as a WMD. That specifically includes bombs, grenades, mines, and small rockets and missiles,” as well as homemade bombs of the sort Tsarnaev allegedly constructed.

Some of the only devices that do not qualify as WMDs are flares, pyrotechnics, and firearms with a barrel less than one-half inch in diameter.  Incidentally, the FBI did also find pyrotechnics in Tsarnaev’s apartment.

Killing someone with a weapon of mass destruction is a capital offense only under certain circumstances, such as when “the offense, or the results of the offense, affect interstate or foreign commerce,” a condition which would appear to have been met in the case of the Boston Marathon bombings.

Oklahoma City bomber Timothy McVeigh was also charged with use of a weapon of mass destruction and sentenced to death.  He was executed by lethal injection on June 11, 2001, at a federal prison in Terre Haute, Indiana.

-Aaron Wallechinsky, Noel Brinkerhoff

To Learn More:

Did the Boston Bombers Really Use WMD? (by Michael Crowley, Time)

Here’s Why Tsarnaev Was Charged With Using a ‘Weapon of Mass Destruction’ (by Spencer Ackerman, Wired)

Federal Government Redefines Rocket-Propelled Grenade as “Weapon of Mass Destruction” (by Matt Bewig, AllGov)