Very few generals or police chiefs would be prepared to act as a test target for called non-lethal weapons. People regularly get killed by rubber bullets.
Today’s invention is a way to make such weapons, if they must be used, actually incapable of causing death.
This involves adapting a conventional ‘riot gun’ in order to propel its projectile using compressed air. It would probably need to be fed from a cylinder on a small trolley (thus limiting the ability of forces to pursue individuals in a crowd at pace).
The weapon would be equipped with a range finder (probably a stereo vision device, rather than acoustic, given the background noise in the average street-level contretemps). Once having determined the range of an individual, the pressure delivered to the chamber, behind the baton round, would be increased or decreased in order to ensure that the impact speed would be constant -and always less than a dangerous velocity.
I’d be keen to see the use of rotten potatoes, whose aerodynamics is pretty straightforward to predict and whose lethality is inherently limited.