An unofficial ban on WA field umpires overseeing West Coast matches is set to be lifted with the appointment of at least one local in Sunday’s western derby.

However, it remains to be seen if the Eagles will operate under the jurisdiction of WA umpires in matches against interstate opposition again this season following consternation over their free-kick dominance.

The standard of umpiring in Perth, particularly at West Coast home matches, has come under intense scrutiny this year amid criticism surrounding the alleged influence the partisan home crowd has on decision making and free-kick counts.

St Kilda coach Alan Richardson said in June, after the Saints’ second match at the stadium, that the “noise of affirmation” — a phrase he coined last year to describe the crowd’s impact — had gone to a new level because of larger attendances at Optus Stadium compared to Subiaco Oval.

The following week, former AFL umpires boss Peter Schwab led calls by some high-profile figures in the game for the league to look into free-kick tallies in Perth.

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The public uproar peaked after the West Coast-Essendon clash in round 14, when the Bombers won by 28 points but lost the free-kick count 33-17.

WA whistleblowers Nathan Williamson, Jeff Dalgleish and Dean Margetts officiated in that match alongside Victoria’s Craig Fleer under a trial of the four-umpire system.

Current AFL umpires coach Hayden Kennedy later confirmed the league would investigate the trends behind the persistent pattern of West Coast’s free-kick dominance in Perth, which statistics showed had run over several seasons.

The AFL umpiring department has not released its findings publicly and the league declined to comment when contacted by The West Australian yesterday.

However, not one WA field umpire has officiated in any of West Coast’s five matches, in Perth or interstate, since the controversy in round 14.

More than one third of field umpires (eight of 22) in seven Eagles home matches before round 15 were from WA.

Camera Icon PERTH, AUSTRALIA - MARCH 25: Umpire Nick Foot practices a centre bounce during the 2018 AFL round 01 match between the West Coast Eagles and the Sydney Swans at Optus Stadium on March 25, 2018 in Perth, Australia. (Photo by Will RussellAFL Media) Credit: AFL Media

The West Australian understands the umpiring department made a decision to deploy teams consisting mainly of interstate umpires in Perth to investigate what effect it would have on free-kick counts.

WA whistleblowers made up 32.5 per cent of field umpires (13 of 40) in all West Coast and Fremantle matches at Optus Stadium that featured interstate opponents in rounds 1-14. That figured dropped to 13.3 per cent (two of 15) in rounds 15-19.

Dalgleish was the only local umpire appointed in Perth in the past five weeks.

He officiated in Fremantle’s recent home matches against Brisbane (round 15) and Hawthorn (round 19).

West Coast’s average free-kick differential in Perth against interstate sides has dropped dramatically from +9.3 before the umpiring department’s investigation was launched to +1.0 in two matches since.

But those figures included a 28-20 free-kick count in Sydney’s favour in round one when two WA umpires were in charge and a 30-13 tally in the Eagles’ favour against Port Adelaide with no WA umpire on the field.

Fremantle’s average free-kick differential in Perth against interstate sides has risen from -3.5 before the investigation was launched to +5.7 in three matches since.

West Coast have not lost a free-kick count at any venue since round 10 and have received fewer free kicks than their opponents in only four matches this season.

Overall, the Eagles rank third for free-kick differential (+3.7) behind Collingwood (+4.6) and North Melbourne (+3.9). Fremantle (-1.2) rank 12th and top team Richmond (-5.1) are 18th.

The AFL will confirm its umpire appointments on Friday.