Dale Myers, whose fantastic book With Malice is the gold standard on Lee Harvey Oswald's murder of officer JD Tippit, has put together an excellent debunking of John Armstrong's Harvey and Lee theory as it relates to that crime.
Myers uses his encyclopedic knowledge of the Tippit case to destroy Armstrong's assertions and provides extensive examples of Armstrong "cherry picking" facts and misrepresenting evidence to the point of changing quotations to suit his needs. Highly recommended.