What do you think?
The Green Goblin abducts Peter's girlfriend, Gwen Stacy, and lures Spider-Man to a tower of either the Brooklyn Bridge (as depicted in the art) or the George Washington Bridge (as given in the text).The Goblin and Spider-Man clash, and the Goblin hurls Stacy off the bridge. Spider-Man shoots a web strand at her legs and catches her. As he pulls her up, he thinks he has saved her. However, he quickly realizes she is dead.
The original comic features a "snap" sound effect next to Gwen Stacy's head in the panel in which Spider-Man's webbing catches her, however some later reprints remove the effect.
In The Amazing Spider-Man #125 (Oct. 1973), Marvel Comics editor Roy Thomas wrote in the letters column that "it saddens us to have to say that the whiplash effect she underwent when Spidey's webbing stopped her so suddenly was, in fact, what killed her. In short, it was impossible for Peter to save her. He couldn't have swung down in time; the action he did take resulted in her death; if he had done nothing, she still would certainly have perished. There was no way out."
In the History Channel special Spider-Man Tech, Stan Lee suggests that her neck may have indeed been snapped.
Physicist and comic collector James Kakalios, in his book The Physics of Superheroes, states that in the real world, the whiplash effect would have killed her.
For some time, however, fans speculated that the shock of the fall itself caused Gwen Stacy's death, due to the Green Goblin telling Spider-Man in The Amazing Spider-Man #121, "Romantic idiot! She was dead before your webbing reached her! A fall from that height would kill anyone — before they struck the ground!"
So who killed Gwen Stacy Green Goblin or Spider Man?