Video Assistant Referee (VAR) causes controversy every week in the Premier League, but how are decisions made and are they correct?
After each weekend, we take a look at the most high-profile incidents and examine the process both in terms of VAR protocol and the Laws of the Game.
VAR overturn: Penalty for handball by Iwobi
VAR decision: Handball against Iwobi, with the penalty scored by Martinelli.
VAR Review: This comes down to how handball is judged after the law was changed to a point on the upper arm, rather than the armpit. It has made judging a handball offence much more difficult and at times inconsistent.
We can look at a number of incidents this season, with the ball hitting the arm around the same place. It depends on the subjective opinion of the VAR, in this case Lee Mason, whether the ball has hit above or below the point of a handball offence.
For instance, for a throw-in the whole of the ball has to be over the whole of the line. But for a handball offence, does the whole of the ball have to be over the undefined position on the arm? This remains unclear, but in the Premier League referees try to use the ball hitting the badge or sponsor's logo as being no offence -- but this still relies on the VAR making that call.
In terms of Iwobi, he leant into the shot and the contact on the arm appears low enough for a penalty to be a correct VAR decision. But that doesn't mean this is consistent with some past cases where handball wasn't given. And Everton know all too well about this.
In February, Frank Lampard's side were denied a penalty by the VAR, Chris Kavanagh, for a Rodri handball. The score was 1-0 to Manchester City late in the game, meaning Everton were denied the chance to claim a point from the penalty spot. Kavanagh decided other available angles made the evidence inconclusive, but it led to PGMOL, the body that controls refereeing in the Premier League, apologising to Everton for the mistake.
One issue has been referees influenced by previous VAR decisions, rather than the evidence which presents itself. Just 13 days prior to the Rodri decision, Kavanagh was also the VAR when he decided there wasn't conclusive proof that Craig Dawson had committed a handball offence when scoring a late equaliser in a 2-2 draw for West Ham United at Leicester City.
This goal should, on balance, have been disallowed. In this case, too, Kavanagh had found another angle which cast doubt on a VAR intervention, so he allowed the goal to stand. It's highly likely that this decision influenced Kavanagh when the Rodri decision came along.
Iwobi, Rodri and Dawson should all have been given as handball offences. It comes down to inconsistency in VAR decision-making, which will always be apparent to some degree because of the subjective nature of decisions. However, it feels as though the Premier League's "high threshold" for interventions -- combined with a clear reluctance for referees to reject reviews at the monitor -- is a barrier to better consistency.
Possible penalty: Foul by Konate on Gomes
What happened: With the scores locked at 1-1 just after half-time, Wolves' Rayan Ait-Nouri swung a free kick into the area which Tote Gomes tried to get on the end of, but he appeared to be pushed by Liverpool defender Ibrahima Konate.
VAR decision: The VAR, Stuart Attwell, decided there wasn't enough in the incident to view it as a clear and obvious error by the referee, Anthony Taylor.
VAR review: There was a clear use of the shoulder by Konate into the back of the Wolverhampton Wanderers player, and there's absolutely no doubt that the penalty would have stood if awarded by the referee.
Plenty of fans will believe this should have been a VAR penalty to Wolves, and maybe if Liverpool had won the title ahead of Man City the incident would have got more attention. It's also possible Konate could have been sent off for denying a goal-scoring opportunity.
We've talked about past incidents influencing referees in the VAR room and it may well fit here too, in terms of enforcing a high threshold for an overturn.
Attwell was the VAR last Tuesday when Southampton's goal was allowed to stand against Liverpool. Again, it was not considered a clear and obvious error to disallow that goal after what seemed a certain foul in the build-up by Lyanco on Diogo Jota.
At least you can say the threshold is consistently high, but few would accept it's consistently right in these two cases. One against Liverpool, and the other in their favour.
In both cases the referee had a clear view of the incident, a contributing factor in the on-field decision being unchanged.
What happened: It was goalless when Jamie Vardy went down injured in the middle of the pitch as Southampton had the ball. Referee Jon Moss gave the dropped ball to Leicester City, and the Foxes scored directly from it through James Maddison.
VAR decision: The VAR is unable to intervene.
VAR review: This is purely a refereeing error by Moss, who was taking charge of his last game before retirement. As Southampton were in control of the ball when the play stopped, it should have been returned to them.
However, Moss appeared to get mixed up as it was a Leicester player who was down injured, and gave the ball to the home team.
But the VAR is unable to intervene on any kind of restart (other than on a penalty kick), which includes the ball being out of the quadrant on a corner kick, or a foul throw. Even though the referee made a clear error, the goal has to stand.
Meanwhile, the penalty given to Southampton wasn't overturned as there was not clear and obvious error by the referee. Youri Tielemans stuck out a leg and while the contact came largely from the running momentum of Stuart Armstrong, this would not be considered a mistake by the VAR.
VAR overturn: Gelhardt goal ruled out for offside
VAR decision: Offside, goal disallowed.
VAR review: One of the more simple offside decisions for the VAR, who was John Brooks. From the first angle showed in the television coverage, you could see it was likely that Gelhardt was in advance of the last defender.
Some fans had questioned the use of a different angle to display the decision, claiming that the camera was not square to the players. But this is a common misconception about the way the Hawk-Eye offside technology works. Whichever camera is used, the technology is mapped to the pitch and this takes into account the angle. That said, in this instance it was perhaps obvious from the first angle than the one the VAR chose to use to apply the lines.
Information provided by the Premier League and PGMOL was used in this story.