How to Identify a Meth Lab

Mark sent me these instructions:

As a law enforcement officer I have been approached by several people lately wanting to know how to identify a Meth Lab.

Here is a picture of four Labs. I think it's pretty obvious which one is the Meth Lab. I hope this helps. 

Let me know if I can be of any further service in this matter.

Update March 2016 replaced missing picture.