Your mother needs to understand that polygraph "testing" has no scientific basis. Here are two articles that you can print out for her:
http://antipolygraph.org/articles/article-018.shtml
http://antipolygraph.org/articles/article-028.shtml
A poster that briefly explains why honest people often fail the polygraph is available here:
http://antipolygraph.org/publicity/campus-poster-005.pdf
For further reading on the scientific shortcomings of polygraphy, see Chapter 1 of The Lie Behind the Lie Detector:
http://antipolygraph.org/lie-behind-the-lie-detector.pdf
Your mother also needs to know that many other truthful people have been wrongly branded as liars by the polygraph. Chapter 2 of the above book provides numerous examples, and you'll find public statements by other polygraph victims here:
http://antipolygraph.org/statements.shtml
"Be aware that polygraph operators also read the discussions on this message board. If you wish to remain anonymous, be careful not to post enough personal detail that you could be identified (for example, the exact date of your polygraph examination"
Just read that and got a little worried.Anyways, thanks for the links, i apprecate it.