Question: Can any one make fake sex movies of any person , if yes how can you tell it is fake.? 

Answer: I don't think you are talking about movies as in hollywood .I think you are talking about making a fake video of some one having sex.  Yes it can be done with proper editing and including other porn movie scenes. The way to catch the editing parts is to view the movie and watch for irregularities. You can also watch it frame by frame to check for abrupt changes. Some times the lightning of one scene is different from another.
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