...oh, I was not joking at all in my previous post - for I suppose with some reason that it is quite rare to be told such clearly by a native japanese "hey, you, SMALL MIND!"... ...anyway, a native will be far more useful...
It means something along the lines of, "you're a little bit dumb" or "you're a little bit stupid." Atama warui = stupid. It doesn't mean weird, crazy, or perverted. There are other words we'd use for those: atama okashii, kawatteru, kurutteru, sukebe, etc.
we don't use honorific お with such abstract words as 特定、鑑定、結果、調査、etc. (counterparts in English for instance: words derived from latin) but this is not a rigid rule, there seems no rigid rule to tell which honorific お or 、ご（御） to use with a noun. For example, you could say ご飯 but not お飯, while お花見 is good but not ご花見。You could say ご苦労 but not お苦労. It must be really annoying for learners of Japanese, you've got to learn them one by one.
Also, using 特定 is not good, it's like saying "I'm infatuated" to your girlfriend. 解決 sounds better.