"It's fifty-fifty, it leaves you with no possible way of knowing did she discuss it with him or didn't she discuss it with him," Giuliani said, in a radio interview with Geraldo Rivera that was reported by Capital New York.
Christie has repeatedly denied any knowledge of the closures and fired Kelly when her emails were revealed.
Some Democrats have alleged Christie's allies ordered the closures to retaliate against a Fort Lee's mayor, who declined to endorse the governor's re-election bid.
Though he indicated he believes Christie may have known about the order, Giuliani also offered some kind words for the governor.
"I like Chris very much and he's being unfairly treated, and he's a good friend," said Giuliani.