xpmachina,

I think Pantywaife's suggestion that you simply tell the DA that your lawyer has advised you not to submit to a polygraph "test" is better than my suggestion that you explain to the DA that you've learned that the "test" is a fraud. You shouldn't have to explain at any length your decision to refuse the polygraph, and the short explanation that you've refused it on the advice of your lawyer should be adequate.

By the way, if your lawyer suggests that you should take a polygraph "test," you should fire him and get a smarter lawyer.