How would I know? 我怎么知道？

None of my business. 不关我的事。

I'm innocent. 我是清白的。

You've got the wrong person. 你们找错人了。

I know nothing about this. 我对此一无所知。

It's nothing to do with me. 这事跟我无关。

I was wronged. 我是被冤枉的。

It's not my job. 那跟我无关。

I didn't do it. 不是我干的。

I didn't do it on purpose. 我不是故意的。

I was forced to do it. 我是被迫那样做的。

I was threatened by a gun. 我是被枪指着才那样做的。