^ Absolutely correct.
In California, setting a booby trap is a felony, and mere possession of one is a wobbler (can be charged as a felony or a misdemeanor). Check out the code section below. I don't know for sure, but my guess is that the same rule California uses is the majority rule in the country. What the code section doesn't state is what you're charged with if your booby trap kills someone: murder.
If you're looking for a rationale behind these laws that goes beyond the idea that deadly force should not be used merely to protect property, think about this: a booby trap cannot distinguish between persons. The same trap that will hurt or kill a burglar will also hurt or kill a firefighter, police offer, or curious child who opens the door for whatever reason.
CALIFORNIA CODES
PENAL CODE
SECTION 12355
12355. (a) Except as provided in Chapter 2.5 (commencing with
Section 12301), any person who assembles, maintains, places, or
causes to be placed a boobytrap device as described in subdivision
(c) is guilty of a felony punishable by imprisonment in the state
prison for two, three, or five years.
(b) Possession of any device with the intent to use the device as
a boobytrap is punishable by imprisonment in state prison, or in a
county jail not exceeding one year, or by a fine not exceeding five
thousand dollars ($5,000), or by both that fine and imprisonment.
(c) For purposes of this section, "boobytrap" means any concealed
or camouflaged device designed to cause great bodily injury when
triggered by an action of any unsuspecting person coming across the
device. Boobytraps may include, but are not limited to, guns,
ammunition, or explosive devices attached to trip wires or other
triggering mechanisms, sharpened stakes, and lines or wire with hooks
attached.