best of my knowledge
When someone is asked a question, but doesn't want to reveal the truth. Therefore reverts back to the common bullshit answer of to the "best of my knowledge". This phrase was made famous by Michael Jackson's doctor on Larry King
Example:
"Larry King: Are you the father?"
"Michael Jackson's Doctor: To the best of my knowledge...no?"
"Larry King: Are you the father?"
"Michael Jackson's Doctor: To the best of my knowledge...no?"