Ways of revising requirements

Steve McConnell, in his book 'How Much Does a Software Project Cost' and World Statistics, tells us that it is most expensive to correct bugs made during the requirements gathering and design phases. Sometimes the bugs detected are serious enough to require redesigning not only your system (or some part of it) but also related systems. When these bugs are detected at the testing stage, the work of analysts, developers, testers and technical writers goes in the bin. 

Can we identify at least some of these bugs at an earlier stage of work? Can a tester (requirements engineer) detect bugs in requirements before software development? 

We will look at one of the fundamental properties of requirements: completeness, including CRUDL. We will see how we can check this property.