Why won't you share his name? The D.A. was a public servant. Not only should his actions taken under the color of his role be public knowledge, but he should be held responsible for them by the public as well. It'd be like saying "I used to work for a President who made Executive Order X", and then being evasive when someone asks who the President was.
There are a lot more possibilities than just those six. It could be almost anywhere, really. For example, how about somewhere in Florida? There have been lots of foreclosures there, and it has a large conservative population.
Also, the poster said "conservative" but didn't explicitly say "Republican", so you can't necessarily rule out counties with Democratic DAs. The poster also didn't give a timeframe. It could have been well before the housing bust for all we know. They were obviously being intentionally vague.
Shouldn't be too hard to find, he gave a lot of unique information. We know that this was in the 2009-2011 timeframe, as this "was a bad time to file a lawsuit in that county".
Here's a checklist of things that shouldn't be too hard to establish with some Google-fu:
* Election results for "double-digit" losses by incumbent DAs.
* Areas with a special division for "mentally disordered" clients (Is this a common term found everywhere? Dunno).
* A (state?, unlikely, but I don't know of many county-level legislatures; they are generally governed by a mayor or council) legislature that started specifically evacuating drug possession cases from the docket (would this count as a "legislative pardon" or were the cases just reset?) as a response to 5+ year lag on civil suits.
* "heavily conservative", which your list here seems to contemplate.
* a sex-scandal embroiled DA, with reports probably emerging in the 2008-2009 timeframe.
And there were other significant details in there too, but I think the sex scandal thing will be one of the best filters. Probably all you need is DAs-in-sex-scandals + election results from 2009-2011 to pinpoint the county. OP was not being sneaky or anonymous at all, anyone who cares can find out relatively easily.