One of the arguments for allowing people to keep handguns is that these are needed for home defence purposes. There are (usually) legal limits, however, to what a householder can do to defend themselves and their property.
One of the common indicators to a court of an appropriate defensive response to being attacked is when the self-defender can prove that they tried their best to get away and avoid physical violence.
Today’s invention is a low-velocity handgun round for home defence purposes. As well as a reduced charge, each such round contains a small accelerometer sealed inside. This will only allow a bullet to be fired if it has first been moving in a backwards direction for some prespecified interval.
Such bullets are therefore very difficult to use in any attack, so that anyone attempting to buy the ordinary sort can be identified as having some kind of offensive behaviour in mind (without limiting anyone’s legal rights to carry weapons).