DH brings children home after a lovely afternoon at the park. A couple of hours later I notice DS's jeans are filthy, take them off to wash and then am hit by the smell of crap.
Further sniff test on offending brown patch reveals that it's not dog crap either (well educated on the subject after 3 DC and a dog) am mortified. Quiz DH about where DS was playing and he confirms he was in the children's bark area the whole time.
If it's not a yob/drunk type then maybe someone's small child? but would let your DC relieve themselves and then leave a turd slap bang where children are playing?