Image of the presidential limousine on Main Street

Notice the driver's door open on the presidential limousine. This tactic was used in heavily crowded areas to move spectators farther back from the motorcade. This was necessary since, as seen in this photograph, the car stayed to the left, keeping President Kennedy as far away from the crowds as possible. This put Mrs. Kennedy, in the words of U.S. Secret Service agent Clint Hill, "in a jeopardizing position." Hill, as seen here, rode on the back of the presidential limousine whenever he felt that the crowds were too close to Mrs. Kennedy. - Stephen Fagin, Curator   

Notice how the president's coat was bunched up near his neck.  The president wore a back brace that caused his jacket to ride up. The unnatural shifting of the coat to a higher-than-normal position caused investigators and conspiracy theorists some confusion when trying to line up the bullet hole in the coat with the entry hole in Kennedy's body.  With the coat in its normal position, one might mistakenly conclude the hole was actually lower on his body.  Such differences are part of the Single Bullet Theory, which is both lauded and derided by those who study the assassination.  - Gary Mack, Curator