Test cases from requirements specifications and use cases

If I were on a project where both requirements specifications and use cases were created, I would expect that I...

would use both for creating test cases. Each provides a different view of what the application should be doing, how it's used, and what the intended product should look like. Both are critically important to my testing, and both would probably have equal weight in my testing process.

Software testing resources: How to design test cases from use cases How to design test cases Software testing deliverables: From test plans to status reports

As for traceability, if that's a requirement, the best person to ask is the auditor who will be ensuring compliance. If you're working in an environment where traceability is important, then I would assume you would want to trace your test cases back to both sets of artifacts, but the best way to be sure is to ask.