Umm, they didn't "continue" to take lie detector tests or "pass them all."
They refused and refused and refused to take any polygraph tests at all, even went to court to not have to take them. Years later, they paid a polygrapher to administer a private test to each of them, with only 3 questions on it.
Patsy had several inconclusives - John passed the simple test. They had a huge press conference to announce the private results and failed to mention the two days it took Patsy to pass the test and the several inconclusives she had first. They didn't even allow the first polygrapher (yes, it took two) to make a statement - his name had to be pulled out of them, at that.
It was all exceedingly dishonest. Lin Wood even lied about it to the public.
Funny, they passed lie detector tests and asked for even more. Damn those pesky facts.
http://transcripts.cnn.com/TRANSCRIPTS/0005/24/se.02.html
Experts Say Ramseys Passed Lie Detector Tests
http://denver.rockymountainnews.com/extra/ramsey/0429ramse1.shtml
John and Patsy Ramsey went on national television Friday to say they are willing to take a lie detector test, but the test must be given by someone selected by their lawyers.
http://www.crimelibrary.com/notorious_murders/famous/ramsey/time_11.html
On May 24, John and Patsy Ramsey underwent lie-detector tests conducted by Ed Gelb and announced that the findings had cleared them of any involvement in their daughters death. (with even more information on the link including the questions asked of the Ramseys and detailing who, when and where this test was conducted, including it's authentication)