I am wondering why there were turret guns inside the trench on the Death Star if its designers had not considered small one-man fighters to be a threat.
"General Dodonna : The battle station is heavily shielded and carries a firepower greater than half the star fleet. Its defenses are designed around a direct, large-scale assault. A small one-man fighter should be able to penetrate the outer defense.
Gold Leader : Pardon me for asking, sir, but what good are snub fighters going to be against that?
General Dodonna : Well, the Empire doesn't consider a small one-man fighter to be any threat, or they'd have a tighter defense..."
Here are some screen shots of the turret guns inside of the trench. These screen shots show that the turret guns are located on the floor of the trench and that the laser bolts being shot at the X-wing fighters are coming from these trench floor turret guns.
Why were there turret guns inside the trench on the Death Star?