The Lindsay Clancy Trial Sketch by Robert Exter PLYMOUTH, Mass. — A Massachusetts jury spent seven days trying to decide whether Lindsay Clancy was criminally responsible when she strangled her three children. It could not. On Sept. 4, Superior Court Judge William F. Sullivan declared a mistrial. The charges remain. So does the fight over what the record actually shows — and over what kind of story the public thinks it has been watching. Clancy, 36, a former labor-and-deliver