Patent lawsuits are filed in federal court. There are jurisdiction rules, and even recent attempts to curtail the practice of forum shopping, but now that many patent trolls make their home in Marshall, Texas, it's rather difficult to avoid that forum. They will more or less say that due to the fact that the troll has set up shop in Texas, any other jurisdiction is as good as here, so you're stuck with Texas.
In short, the trolls do everything they can to make you fight them in their home court. Enough so that it makes the news whenever people find a new legal trick to escape. Many such tricks have failed. One example that springs to mind is that one troll who filed a day earlier than anyone else would be able to, because they used tricky local rules to get a cover sheet while technically filing just after midnight. But because they were first, they got to choose to stay in Marshall, TX.