Question: What are the best ways to translate `For all you know`?

For example:

> 
> For all you know, she could be lying to you.
> 
> 
> In response to a friend getting upset that her friend isn't picking up her phone, I respond, "For all you know, something could have happened."
> 
> 
> A neighbor sends us some vegetables and I tell my wife, "We better wash them first, for all we know, they could be covered in pesticide"
> 
> 
>

Answer: 
Agree with StumpyJoePete. 

As we all know = Everybody knows.

For all you know = You don't really know for sure. 

I think Damian Siniakowicz's suggestion will work. 

We better wash the vegetables first, for all we know, they could be covered in pesticide

我们还是先把蔬菜洗一下，说不定有農藥呢。

A couple more suggestions:

我们还是先把蔬菜洗一下，誰知道有沒有農藥呢？

我们还是先把蔬菜洗一下，可能有農藥呢。
For all you know, she could be lying to you.

听你所见,她可有在骗你.