Video Assistant Referee 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 major incidents, to examine and explain the process both in terms of VAR protocol and the Laws of the Game.
In this week's VAR Review: Should Everton's Yerry Mina have been sent off for "biting" AFC Bournemouth's Dominic Solanke? Were Brentford denied a penalty against Manchester City? And should Chelsea have been given a late spot kick against Newcastle United?
Possible red card: Mina on Solanke
What happened: In the 69th minute, Dominic Solanke got involved in an altercation with with Everton goalkeeper Jordan Pickford on the goal-line. That resulted in a melee involving a number of players, with Everton defender Yerry Mina clashing with the Bournemouth striker inside the goal. Referee Stuart Attwell booked Pickford and Solanke, and also Adam Smith for dissent, but took no action against Mina -- though the VAR, Michael Oliver, was able to check it.
VAR decision: No red card.
VAR review: Solanke pulled down his shirt to show Attwell a mark on his chest, but there was no chance the referee would be able to see the incident himself properly. It's then a question of the VAR finding evidence of an offence worthy of a red card.
Mina does lean his head in towards Solanke's body, but there's nothing in the replays -- either from the regular television angle or the one within the goal -- which suggested a bite. Perhaps the Everton defender nipped at Solanke's chest during the tussle, but there's no proof that the Colombia international committed a red-card offence.
Possible penalty: Gomez challenge on Mee
What happened: The first of two penalty claims in quick succession in the 54th minute, both involving Ben Mee. In the first incident, Kalvin Phillips tried to head the ball away, but it came off his shoulder and dropped towards Mee; the Brentford player went to ground under a challenge from Sergio Gomez.
VAR decision: No penalty.
VAR review: We have seen this kind of incident several times in the Premier League this season, and if the referee hasn't awarded any offence, the VAR hasn't gotten involved.
Both Mee and Gomez challenged for a bouncing ball that wasn't under the control of either player, and while the Brentford player might have got a touch on the ball first, it wouldn't be viewed as a clear and obvious error not to give the penalty.
Other similar examples include the challenge by Bournemouth's Marcos Senesi on Arsenal's Takehiro Tomiyasu, and Manchester United midfielder Bruno Fernandes going to ground when challenging with Newcastle defender Fabian Schar. The Independent Key Incidents Panel, which assesses all incidents in the days after a game, agreed both of these incidents were not VAR penalties, and will do the same with Mee, too.
Possible penalty: Handball by Lewis
What happened: Brentford worked the ball back into the box through Vitaly Janelt to Mee, and as the latter attempted to help the ball towards goal, it hit the arm of Manchester City defender Rico Lewis. The loose ball fell to Ethan Pinnock, who saw his shot saved by Ederson, and referee John Brooks then gave a foul on the goalkeeper. Mee immediately asked for a penalty, which the VAR, Darren Bond, then checked.
VAR decision: No penalty.
VAR review: A clear case of Lewis putting his arm to the ground to support his body, which is one of the key exemptions in the handball law. Had Lewis moved his arm into the path of the ball in a way which was obviously meant to stop its path, then the VAR could have awarded a penalty.
We have two very good case studies for this. First, the handball penalty West Ham United wanted against Liverpool when Thiago stopped the ball with him arm in similar fashion. The Independent Key Incidents Panel judged that the referee and the VAR were correct not to give a penalty.
The other comparison is the penalty not awarded to Chelsea against West Ham, when Tomas Soucek stopped a Conor Gallagher shot with his supporting arm. The difference in this second case was Soucek moved his left hand into the path of the ball with an open palm, clearly a deliberate move to stop the path of the ball. The Independent Panel said this one should have been a spot kick.
The Lewis penalty claim fits with that of Thiago, and the VAR was correct not to advise a penalty review.
Possible disallowed goal: Trippier handball
VAR decision: Goal stands.
VAR review: Nothing for the VAR to look at, but one of the quirks of the modern handball law. While it's an automatic offence for an attacking player to score a goal with their arm/hand, it isn't if the ball goes into the net off a defending player -- and the goal counts.
Possible penalty: Handball by Burn
What happened: In the 78th minute, Sterling had a shot on goal and the ball came off the arm of Newcastle defender Dan Burn. Chelsea players appealed for a penalty, but referee Jarred Gillett ignored the claims. The VAR, Peter Bankes, checked for a possible spot kick.
VAR decision: No penalty.
VAR review: Key to this decision for the VAR is that Burn is retracting his arm from the path of the ball. This is one of the exemptions against a handball offence that should be taken into account.
Burn's left arm isn't extended out from his body, and he is clearly trying to get it out of the path of the ball when the ball strikes it.
Information provided by the Premier League and PGMOL was used in this story.