Urinating in Rental- A new Section 8 tenant strategy

I've got a nightmare on my hands! I have a Sect 8 tenant and have had a few issues (dog, non-pay of electricity, etc) But HUD recently failed my unit twice- once for a ripped window screen and the second time for pee puddling around the stove. The tenant said "it shows up every day". She says it's coming from the stove. Housing Court said I can't evict her yet, even though she hasn't paid her portion for three months. Is throwing pee on a wall to make it look like a leak a new strategy for tenants trying to stall an eviction? She stated "we're not peeing behind the stove!" (Which makes me think she or her 17 year old or her 11 yr old ARE!) Ideas? How does one prove where pee is coming from? (building's drain for waste is a good 30' away and goes straight down, not ‘over'; my unit is ground floor on 2 story building)