harry potter - Did Voldemort know when he was being lied to by Snape?

If Voldemort had ever known -- or even suspected -- that one of his inner circle was using Occlumency against him, I don't think that person would have lived for very long. Therefore, either:

1. Voldemort never tried to use Legilimency against Snape (which I find extremely unlikely; especially since, as stated at the beginning of HBP, Snape had to defend his actions of the past fourteen years after Voldemort's return); or


2. Snape did use Occlumency against Voldemort, but Voldemort was unaware of it.

I lean toward the latter. I'm sure a clumsy beginner's attempt at Occlumency would be easy to spot, but perhaps a skilled-enough Occlumens is able to hide the fact that they're hiding anything -- to leave parts of their mind open while blocking other parts, and leave even a powerful Legilimens like Voldemort none the wiser.

Personally, though, I think that Snape had additional help, beyond even his skill in Occlumency: (spoiler for book 7)

Snape's love for Lily.

Love is the antithesis of everything Voldemort ever stood for; he never understood it, and it actually caused him pain when he possessed Harry in OotP. I think a skilled Occlumens like Snape could turn that to his advantage in steering Voldemort away from any thoughts relating to protecting Harry.

• Next prefixes - Prefix "a" in "amaze"
• Previous doctor who - What happens to Fixed Points if the past is rewritten?