Judge Jonathan Down said while police had been unable to determine the cause of the accident, Watson's criminality lay in his decision to leave the scene.
And this is the point. If Watson had stayed and faced up to the situation, he probably would not be going to jail, but he chose to do something criminal by driving off without even knowing if he had killed the little boy.
Sometimes things happen in life and one has to face them front on and accept the consequences. Watson, who seems to have been influenced by others in the car to drive on, chose not to.
Now he has time to think about his actions and hopefully come out of jail a better man. Hopefully others will learn from this as well.