知らない used in "I don't care"


A:一人で海外行きたいけど。。。反対しても行くよ！！

B:ダメだよ！！何かあったら知らないよ！

When this kind of nuance is used for the verb 知らない, why is the verb 知らない used
even though it means "to know" and how do you translate it exactly...?




You could think of it as " _complicitly knowing_ ".  
So, in the context of your example「知らない」it expresses something like:

  * "I'm not involved", "I won't get involved" 
  * "I don't approve" 
  * "you can't blame it on me" 
  * "it's got nothing to do with me" 

So it could be translated this way...

>   * "If anything happens to you, don't come crying to me about it."
>   * "I can't be held responsible if anything were to happen."
>

Weblio has an entry for 知らない that shows the two usages:

> ある物事に関する知識・情報を有していないこと。  
>  **関与しない** という意思の言明にも用いられる。

<http://www.weblio.jp/content/%E7%9F%A5%E3%82%89%E3%81%AA%E3%81%84>

