Gieschen was referring to the shot at goal that Geelong's Nathan Vardy had early in the second quarter of the Cats' loss to North Melbourne on Friday night.
Vardy's shot was called a goal by the officiating umpire, and it remained a goal even after some replays used by the video officials appeared to show it hitting the post.
"Our goal umpire was directly under the post, in a terrific position to see," Gieschen explained to AFL.com.au.
"He actually didn't see the ball hit the post at all, he didn't hear the ball hit the post, and we had other umpires in the vicinity who said the same thing. They didn't hear or see the ball hit the post.
"So the goal umpire came up and gave a goal signal."
"But our people up in the score review box had an opportunity to see a replay, and they saw that quirky deviation and funny movement of the ball.
"They thought, 'We better check this and see what's happening.'"
North Melbourne coach Brad Scott was left scratching his head when the vision was ruled inconclusive and the original decision was allowed to stand.
"We sent the runner out to tell the boys that … the ball hit the post. It will be a kick in,” Scott told 3AW on Saturday morning.
"I just made a joke in the box. I said to the boys, 'Well, hang on a second, we could easily get Khawajaed here.' And we got Khawajaed."
Scott was referring to the decision on the opening day of the third Ashes Test, in which Australian batsman Usman Khawaja was given out caught behind by the video umpire, despite the replays and hot spot technology showing he had not hit the ball.
Nevertheless, Gieschen is adamant that there was not enough evidence to overturn the goal umpire's original call on Vardy's shot.
"What we need to understand is they have to be 100 per cent certain, 100 per cent clear, that that ball hit the post to overturn the (decision of the) umpires on the field, who believed it didn't hit the post," Gieschen said.
"Yes there appears to be some sort of deviation, but was that the ball dropping in its trajectory? Had that deviation occurred after the post?
"Our people up in the box deemed it was inconclusive, that they couldn't be 100 per cent certain, therefore we go for the umpire's call at the time.
"We're comfortable that that goal stands."
Along with giving his thoughts on the Vardy decision, Gieschen has also spoken exclusively to AFL.com.au about North player Ben Jacobs' decision to play on while still out of bounds.
In addition, he has reviewed the much talked about shepherd laid by Gold Coast's Campbell Brown, the free kick given away by Greater Western Sydney's Jeremy Cameron for not handing the ball back to the umpire quickly enough, and a contentious decision not to penalise Western Bulldog Jason Tutt after he was tackled by Sydney Swan Dane Rampe.
