Dzhokhar Tsarnaev charged with using ‘weapon of mass destruction’ (opens in new tab)

The 'mass' part reflects the principle of damage radiating outward from the origin and affecting whoever/whatever happens to be in proximity, as opposed to the more targeted destruction caused by a bullet or handheld weapon. Of course you could kill multiple people with a handheld weapon or (rarely) hit several people with a single bullet, but in general such attacks involve one-on-one interactions even if there is a series of them in rapid order, as with automatic gunfire. hitting multiple individuals from a single shot or manual attack is considered a fluke.

See notes on http://www.law.cornell.edu/uscode/text/18/2332a and http://www.law.cornell.edu/uscode/text/18/921

Note that the law is not necessarily drafted to reflect the actual probability of injury, but to dissuade any use of the method; explosive, chemical, biological and radioactive attacks are by nature indiscriminate. That's considered much worse than an attack on a particular individual (you could launch an indiscriminate attack by, say, firing a gun into a crowd. But that lack of care about who you hit would itself attract a higher sentence). Furthermore, it radiates temporally; if you plant a device and then drop dead of a heart attack, the device remains dangerous even though you are no longer capable of forming criminal intent. It presents risk from when it's emplaced to when it has finished releasing, a period which could last years. In similar fashion, using a bomb or poison to kill someone automatically makes the offense into Murder in the First Degree, negating defenses like 'crime of passion' or 'heat of the moment'.

http://www.schneier.com/blog/archives/2009/04/definition_of_...

Here's the legal code which describes a "destructive device" (passed in 1968 and amended several times):

http://www.law.cornell.edu/uscode/text/18/921

Note that it is so broadly written that it has to specifically exclude antique muzzle-loading rifles.

Is a gun a weapon of mass destruction? Why not?

Yes, there are grownups in charge of making such laws, and perhaps you might benefit from contemplating the principles behind such laws before projecting your understanding of a term onto the legislative language. 'Weapon of mass destruction' is a categorical definition, not a quantitative one. The quantitative aspect of the case will be reflected in the number of murder/battery charges.

And so further down the Orwellian tunnel of language distortion we go: if we (the good guys of course) do it then it's collateral damage and enhanced interrogation; if they (those evil scum) do it then it's weapons of mass destruction.

I think when people hear WMD they take it to mean nuclear chemical and biological weapons capable of killing thousands in an instant or very short space of time. There is no way anyone seriously considers an IED of any crappy variety to be a WMD no matter how it is deployed or what the intent behind the murders is.

But yeah, let's keep on barreling down that road, let's see where it'll take us.

EDIT: as anigbrowl points out the answer is pre: https://news.ycombinator.com/item?id=5591399 Also interestingly mass in this sense means indiscriminate as opposed to targeted. I don't know is it just me or were others under the impression that mass meant on a massive scale. It certainly seems to have been used in that sense in the run-up to Iraq 2003 at which time it entered the public lexicon. And as I say I don't remember any legal-heads piping up to correct the misconception.

It ties in nicely with defining environmental activists who had never killed anybody (and who had taken pains to avoid doing so) as terrorists after 9/11.

I really enjoy a good bit of legal context. No doubt that trained prosecutors do things for legitimate and rational reasons.

However, there is also a role for the "peanut gallery" of uninformed speculation here. In fact, I'd argue the public perception of this stuff is 1000 times more important than the legalese.

You want a crime that's got "mass destruction" in the title, you need to demonstrate to the common man that this involves mass destruction. I don't believe that's too much to ask from the system.