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: Why Brighton & Hove Albion defender Pervis Estupiñán should have been sent off at West Ham, and how Everton goalkeeper Jordan Pickford got very lucky against Chelsea.

West Ham 1-1 Brighton

Possible red card: Estupiñán foul on Kilman

What happened: Max Kilman brought the ball forward in the middle of the pitch in the 84th minute when Pervis Estupiñán attempted to make a challenge. The Brighton & Hove Albion defender fouled Kilman, and referee Rob Jones immediately produced a yellow card. It was checked by the VAR, Paul Tierney.

VAR decision: No red card.

VAR review: Serious foul play has been one of the biggest talking points in recent months. Indeed, referee's chief Howard Webb ran though a number of such challenges in the most recent episode of Match Officials Mic'd Up.

Of the six VAR errors logged by the Premier League's Key Match Incidents (KMI) Panel this season, two have related to serious foul play. First, the wrongly awarded red card for Manchester United's Bruno Fernandes against Tottenham Hotspur, during which the VAR did not intervene. His suspension was overturned on appeal. The second was the controversial VAR dismissal of Brentford's Christian Nørgaard at Everton. Nørgaard's suspension was also canceled through an appeal.

And last season, a quarter of the 24 missed VAR interventions related to serious foul play.

It seems to be an ongoing issue, with a VAR unable to identify when it's right to get involved. The referee may be best suited to judge the force and intensity live on the field, rather than through replays, but he is obviously going to misjudge it from time to time -- and VARs are falling short on this aspect.

While two mistakes have been logged, fans will probably feel that number should be much higher. But the Premier League's desire for greater physicality, compared to other leagues, means challenges with only a small amount of contact won't be judged as a mistake. See Chelsea's Moisés Caicedo vs. Tottenham Hotspur, Brighton's Adam Lallana vs. Liverpool and Man United's Lisandro Martínez vs. Chelsea.

Then there was Martínez's off-the-ground tackle against Crystal Palace -- which looked horrendous but by guidance followed by UEFA and the Premier League should only result in a caution (more on this to come.)

Where does Estupiñán's foul on Kilman fit into the picture?

Sometimes a referee can be too close to assess a situation properly, and that may have happened to Jones. Perhaps he felt Estupiñán was low and force wasn't sufficient. Or maybe as it was one-footed and on the stretch, a yellow card was acceptable. Understandable explanations in basic terms, but there are other aspects that suggest Estupiñán endangered the safety of an opponent, and it should have been a red card.

Martínez wasn't sent off at Palace because the challenge stopped before reaching Daichi Kamada; guidance says that even if a player has two feet off the floor, as Martínez did, you cannot endanger the safety of the opponent if it wasn't possible to touch him.

Estupiñán's tackle doesn't fit into that category, as his momentum didn't stop and Kilman was caught with studs, pushing the shin guard out of place.

Estupiñán's foot came off the floor before hitting Kilman, but it's how you connect with the opponent, not intent, that matters -- just ask Liverpool's Curtis Jones after his VAR red card at Spurs.

Verdict: Estupiñán was off the floor with both feet, meaning he was out of control in the challenge and was unable to stop himself following through into the shin of Kilman. It should have been a VAR red card for serious foul play.

Tierney -- who has been exclusively on VAR this season because of injury -- has been almost flawless on VAR this campaign, according to the KMI Panel. Across 20 appointments through Dec. 16, he had been involved in 42 KMIs (not including factual offsides), markedly more than any other VAR, with no errors, and of the 200 votes cast on his calls, 197 have been for a correct decision and only three against.

However, Tierney was the VAR for the possible red card for Leicester City midfielder Wilfred Ndidi's foul on Chelsea's Cole Palmer. Webb feels this should be a red, even though the KMI Panel voted 4-1 against a VAR intervention from Tierney. And of the six missed VAR interventions for serious foul play last season, Tierney was on VAR for two of them.

Perhaps the VAR who has statistically been one of the best does have an issue picking up serious foul play, or maybe it's a wider issue for how it's officiated in English football.

This will go down as the fourth missed VAR intervention of the campaign.

Everton 0-0 Chelsea

Possible penalty: Pickford challenge on Gusto

What happened: Chelsea won a corner in the 32nd minute, and the delivery went all the way through to Axel Disasi, who headed against the post. The loose ball ran for Malo Gusto, who saw his shot deflected behind. Goalkeeper Jordan Pickford had charged out and clattered into the Chelsea player, but referee Chris Kavanagh decided it was a normal collision and gave the corner. The VAR, Graham Scott, checked for a possible penalty. (Watch here.)

VAR decision: No penalty.

VAR review: It was deemed that Pickford came out to make a save, and as a goalkeeper, Pickford has licence to throw himself in front of a striker. Indeed, he would be expected to make himself as big as possible to stop the shot, and it's rare that you see a goalkeeper penalised following an unavoidable collision when doing so.

But this wasn't the kind of save you usually see from a goalkeeper; Pickford rushed toward Gusto off the ground challenging with his feet, rather than spreading his body. This crosses the line and was at least reckless, and it should have been a yellow card and a penalty. Indeed, there are similarities in nature with his tackle on Virgil van Dijk in October 2020 -- he somehow escaped a VAR red card -- which knocked the Liverpool captain out for the rest of the season.

Verdict: A poor challenge, and he got away with it only because he's a goalkeeper. Kavanagh may not have had a clear view, but this should have been another VAR intervention.

Like Tierney, Scott has worked exclusively as a VAR this season and has even more impressive numbers. Scott has been appointed to 12 matches, has been involved in 23 KMIs (not including factual offsides) and to this point has an immaculate record of 115 votes to nil. Perhaps the KMI Panel will agree that it wasn't a clear and obvious error for the VAR to intervene, but it should have been a spot kick.

Crystal Palace 1-5 Arsenal

Possible red card: Clyne challenge on Calafiori

What happened: Nathaniel Clyne caught Riccardo Calafiori with a late tackle in the 79th minute. The Crystal Palace player was booked by referee Simon Hooper. The VAR, Michael Salisbury, checked for a possible red card.

VAR decision: No red card.

VAR review: Calafiori was caught around the ankle area, with Clyne attempting to block the Arsenal defender playing the ball.

Clyne was stepping into the challenge, rather than stretching or lunging with excessive force.

Verdict: A yellow card is entirely justifiable. It wasn't at the same level as some of the controversial cautions there have been, and this isn't going to result in a VAR intervention.

We can probably add it to the list of challenges some supporters feel should be a red card but will not be through VAR in English football.

Clyne was substituted a minute later, and it won't be the last time we see this after a player is booked for a very poor challenge.

Man United 0-3 Bournemouth

Possible handball: Semenyo in buildup to goal

What happened: Antoine Semenyo scored AFC Bournemouth's third goal in the 63rd minute, but the VAR checked for a possible handball by the player at the start of the move.

VAR decision: Goal stands.

VAR review: Kobbie Mainoo played the ball against Semenyo from close range, enabling the Bournemouth player to take possession.

As this wasn't immediately before the goal -- there were a few passes before the ball came back to Semenyo -- it would have to be a deliberate handball, or the arm extended away from the body.

Semenyo had his arm close to his side, so it was just a question of whether he leaned into the ball as a deliberate movement.

Verdict: The ball probably did hit Semenyo's arm, but any movement seemed to be natural rather than an attempt to take control and it wasn't clear and obvious enough for a VAR intervention.

Some factual parts of this article include information provided by the Premier League and PGMOL.