Why did JFK's motorcade make turns in violation of Secret Service codes?
On those occasions, Secret Service agent Clint Hill ran up to take a position on the left rear step of JFK's car as a precaution.
At the intersection of Main & Houston Streets, the motorcade turned right onto Houston. At this point, Clint Hill had resumed his position on the front left running board of the follow-up car.
This was because there were no crowds spilling out into the street on Houston and because the motorcade would soon be picking up speed to go on the freeway.
At this point, Nellie Connally, wife of Governor of Texas John Connally, sitting in front of Mrs. Kennedy, turned and said to JFK: "Mr. President, you can't say that Dallas doesn't love you."
As their car approached the Texas School Book Depository building, they turned left onto Elm Street.
Warren Commission Photo
The answer is yes according to Jim Marrs in his book Crossfire: The Plot That Killed Kennedy (1989):
*Agents riding on running boards of the President's car, having additional security in the crowds, making sure windows of buildings are secured.
There is no evidence to suggest any of these additional security actions were taken after the motorcade turned onto Houston Street.
The Warren Report (1964) said it was "impossible" to access the Stemmons Freeway by way of Main Street.
The "Kennedy Assassination Website" by John McAdams gives the following detailed explanation:
"The Elm Street approach to the Stemmons Freeway is necessary in order to avoid the traffic hazards which would otherwise exist if right turns were permitted from both Main & Elm into the freeway.
To create this traffic pattern, a concrete barrier between Main and Elm Streets presents an obstacle to a right turn from Main across Elm to the access road to Stemmons Freeway and the Dallas-Fort Worth Turnpike."
If this had been done, the motorcade could have proceeded through the Main-Houston intersection & avoided the turns altogether.
In the "conspiracy" view, JFK was brought into the "killing zone" by making these turns.