Moving into User Research: Establishing Design Guidelines
The best technical writers do user research to understand the audience for their documentation, create user profiles or personas, perform task analyses, and do usability testing to ensure that their documentation meets users’ needs. All of these are activities in which a user researcher engages. Thus, as a technical writer, you can start amassing experience in user research and building a portfolio of user research documentation.
Six, Janet M. UXmatters (2009). Articles>User Experience>Research>Technical Writing