Certain area's of the midwest have different accents. same for the south. people in Ohio speak entirely different from those in Kentucky. Alamaba vs Mississippi. the list goes on and on. some people "wash" there clothes while others "warsh" them. New Yorkers tend to put an ER in place of an A. slice of "pizzer" or Idea is replaced with "Idear" then things with an ending of ER are replaced with an A 
let me call my "motha" Minnesota has an accent different from others. you can hear the accent in Vicky Wilson's voice. you need to dig deep to try and find his accent. some do not have one at all and can be from anywhere..
Well, ethno-linguistics and dialetology are far more sophisticated than that. They solved the Una Bomber case, for one.
Very true about the Unabomber. I've posted about it before. Netflix has a great show on that. Ultimately it was his PhD thesis that helped get him caught. He used language in his manifesto that would only have been used by an academic from the late 60s. If we knew more about what Cooper said, the linguistics approach that Agent Jim Fitzgerald used could work. I'd be curious to see what "Fitz" thinks about the Cooper case.
As for the accent as mentioned in other posts. His lack of accent is one item that has affected the case in a disproportional amount. I for one believed he might have been Canadian, because it made sense. I don't anymore. Many people have no accent (newscasters, midwest, etc.). Or, if you are from the same area as someone, their accent does not sound like an accent, it sounds normal. Or, Cooper could have had a very distinct accent, and therefore chose to not say much on purpose. Safe to say he was probably not from NYC, as that is a tough accent to hide, even years later. Just talk to Bruce. However, my dad is from Queens and he has no accent anymore. It all depends.
As for Cooper being an American Indian. Rough numbers here, but in 1970 the US population was 205 million. The Native American Population was 827,000. It's possible that he was Native American, but is it probable? He had no accent either. There was mass immigration from Eastern and Southern Europe in the late 1800s and early 1900s. Countries in those regions are known for dark skin and "swarthy" complexions. I find it unusual that he was called "swarthy", yet people still say Native American or Latin. When I think of swarthy or olive complexion, I think of the Mediterranean area-Italy, Greece, Spain, maybe of Arab descent, maybe Turkish. Now, that is from growing up in an area of many ethnicities, versus growing up in a very homogeneous area. Just some thoughts.
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