Scared,

If your freedom is really at risk, the prudent course of action would be to refuse the polygraph.  Any lawyer worth his salt would never advise a client to sit for one, especially in a criminal case.  It's never too late to refuse.  

You can find a detailed description of polygraph countermeasures in "The Lie Behind the Lie Detector" available for free at this website.  You may also want to visit Doug Williams website at: www.polygraph.com.  His manual can be downloaded immediately and costs about $50.  My recommendation would be to download both.

AMM