In the Decisive Dozen--the list of the twelve most important learning factors--Content Validity is Rule #1. If you're training your learners on bad content, you're doing more harm than good.
The TSA has apparently broken this rule to the tune of One Billion Dollars, spending money to train TSA agents to read body language--when there is no scientific evidence that people can actually detect liars.
This has to be one of the most costly training errors in the history of training and development! Congratulations TSA officials...
If you want to test your own skill at detecting liars, see this nice NY Times interactive.