I think technical writing is usually associated with engineering or scientific writing. Specialist writers can specialize in sports, wine, politics, etc.

Specialist Reporting
Hello, Donna McLachlan here, welcoming you to Cultures of Journalism. In this program I'll be talking to five specialist journalists about their working briefs. What does it take to be a specialist reporter? Do you need an MBA, for example, to be a finance journalist.

One of the—if not the—main problem or issue with being a specialist journalist is that you do have to keep seeing the same people all the time, so it is the fact that you can't really just ignore ongoing relationships.

ABC current affairs journalist Matt Brown reports for both television and radio. Finance journalist Alan Kohler also writes across different media. How do you adjust the kind of language that you'll be using for all those different audiences?

A very different kind of specialist reporting is that of writing for a regional newspaper.

Lee-Anne Petchell: You very quickly become something of a minor expert in this field, that's for sure. Gold price obviously is what we live by in Kalgoorlie Boulder and in the Goldfields. It's on every street corner. We have flashing signs with the gold price being updated every 15 minute interval. So everybody has to be exposed to the mining industry. It doesn't matter whether one of our reporters is a sports reporter, or whether they're a court reporter—they still need to understand how the mining industry works.

http://www.abc.net.au/rn/learning/lifelong/stories/s1174639....


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Note added at 2 hrs (2006-04-25 03:38:20 GMT)
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Special-interest writer seems to be the preferred term in US English.

You can be a generalist or a specialist in this business. Generalists cover a wide range of news, while “beat” reporters cover sports, entertainment, and other special-interest areas.

http://www.collegeboard.com/csearch/majors_careers/profiles/...

Tamara Sellman is a special-interest writer and container gardener living in Hoffman Estates, IL. She is also the publisher of Cachepot: The Container Vegetable Gardener's Companion and American Harvest: Celebrating The Fresh Fruits And Vegetables Harvested From America's Gardens, Big And Small.

http://www.growingedge.com/magazine/back_issues/view_article...

Robby has written over 30 articles for Better Homes and Garden's Wood magazine as a special interest writer. He now integrates his background in education with knowledge and research on immigrants who settled in the United States in the 18th and 19th centuries, blending them all into each piece of furniture he creates.

http://www.rvp1875.com/bios/robby.html