Google translator will be the end of Spanish Prof

It's past midnight, and I've been grading final papers for my Civilization class all day. I have only two left, but I am exhausted. And annoyed. As a result of being tense, my neck aches. What's the problem? Google translator. I just realized that at least half the papers seemed to have been written in English and then translated using Google translator. Unlike outright plagiarism and Turn it in, I have no way to prove it that diesn't involve a long battle. And I am mad. Google translator is good enough that the essays are legible. But there are little things that it does not catch, and are the giveaway. I am mad because writing is an essential skill. I am mad because I find it almost disrespectful. I am sure they use Google Translator for other Spanish classes, but I take it personally. So far, I am glad that I included a detailed rubric in how I was grading the paper (finally an assessment book that was useful for something). I am marking every mistake and weird linguistic construction, and taking points out in the following categories: grammar, content, clarity. That alone is 15 points less at least. Because I am doing this, I am spending 40 minutes in each essay. And I just design the final to make it very long, all essay questions. It will kill me, but somebody has to teach this kids a lesson. The worst part is that I told them at the beginning of the semester that I can detect Google Translator very easily. Apparently, they don't believe anybody older than them. Grrr...