Private polygraphers do not say their client "failed" a polygraph. They use the term "inconclusive" instead. Otherwise, they wouldn't get paid. People do not pay to fail a polygraph. Patsy took several poly's with her first polygrapher but all were 'inconclusive'.
If the Ramseys actually *failed* polygraphs, we don't know about it for certain. Inconclusive is not the same as a fail. Inconclusive means the polygrapher cannot say pass or fail.