THE AFL has conceded it was a mistake to overturn Jack Ziebell's goal during Sunday's North Melbourne-Melbourne clash. 

However, League football operations boss Mark Evans has backed the video review process that led up to the decision. 

The goal umpire believed the Kangaroos' midfielder had kicked the goal from 55m, but called for a score review to ensure it wasn't touched on the goal-line.

After 75 seconds of assessing the vision from several angles, the reviewer deemed the ball had hit the post, much to the bewilderment of the crowd and senior coaches Brad Scott and Paul Roos.

There have been 58 score reviews this season with just nine scores overturned. The decision to overturn Ziebell's goal is the first of those nine to be deemed an error. 

"The procedures were correct," Evans said on Monday.

"The umpire is right on the line assessing for a touched ball or not and then calls for a review on the opposite post. But what we say to the reviewer is, it has to be beyond reasonable doubt."

The debate around the score review system has gone on for most of the season with the AFL installing goal-line technology in goal posts mid-season.

The accuracy of the review system has improved in the past 12 months, jumping from 53 per cent last year to 75 per cent in 2014.

While Evans said there had been huge improvements in the accuracy of the system, it was still not perfect.

"If we can improve that 75 per cent to up to 80-85 per cent I think would be around the right mark," he said.

"So far we've installed the goal-line cameras here at the MCG and at Etihad. We've had five reviews in that time; four of them have actually helped us a bit. 

"But as we see more examples there we'll get a better answer out of whether it was touched before or after the line or whether it was a proper kick. 

"The difficult ones for this system is whether the ball was touched off the boot or in flight, or whether it feathers the post. That will be difficult for us to solve that unless we had 50 cameras behind the goal."

In contrast to the Ziebell incident, Evans said the correct decision was made with Essendon forward Ben Howlett's goal against Adelaide on Saturday night.

On replay, one angle appears to show the ball deviate as it brushes past the goal post.

While a public score review wasn't held, Evans revealed that since round seven, every goal in every game has been reviewed as the ball is returned to the centre of the ground.

"I fully understand how the Essendon goal did not get overturned," Evans said.

"There was no vision there to show beyond reasonable doubt that it had hit the post.

"If you look at all of the different angles, I think you'll say it looks like in some of them it hasn't hit the post, but when you look at one camera angle you can get some distortion in the angle. 

"Sometimes commentary teams are very quick to make the call; we're talking about having beyond reasonable doubt. I've looked at it for 15 minutes this morning and I don't think it hits the post."