Smelly Trouble on Third Street

A Third Street neighbor just wrote in with news of a rather unpleasant—and mysterious—crime:

usually it's good news, but this times I have a complaint that i hope you can share. 
someone
on our block has been throwing used diapers in the back yard, behind
our building (457 Street) and the abandoned one on 2nd street (address
not readily at hand).  it's a health hazard, and just plain gross.  we
don't know who it is, but someone around here does.