What a video review may and may not change

Four categories and nothing else

Video review is limited to goals and the events leading to them, penalty decisions, direct red cards, and cases of mistaken identity. Everything outside those categories stays with the referee regardless of how consequential it looks or how clearly the footage shows an error. A second yellow card cannot be reviewed, which is why an obvious mistake in that situation stands while a comparable one in a red-card case does not.

The categories were chosen because each is match-changing in a discrete way that can be examined without unravelling a long passage of play. Knowing the list is usually enough to explain why a particular incident was never looked at in the first place.

The threshold for intervention

The system is designed to correct clear and obvious errors rather than to arrive at the best available decision on every contested incident. That threshold means a review can conclude the original decision was probably wrong and still leave it standing untouched. The reasoning is that a lower threshold would turn every piece of contact into a review and would relocate the decision away from the field entirely.

It also protects the referee in the categories where judgement rather than fact is doing most of the work. Most public frustration with the system is really frustration with this threshold rather than with the technology behind it.

Factual calls and judgement calls

Some reviewable matters are close to factual, such as whether the ball crossed a line or whether an offence occurred inside the penalty area. Others are irreducibly matters of judgement, including the severity of a challenge and whether contact was sufficient to cause the fall that followed. The same review process handles both, which is why outcomes feel inconsistent to viewers who expect a purely factual instrument.

On factual questions the review effectively replaces the on-field decision, while on judgement questions it only checks whether that decision was defensible. Separating the two categories explains most of the apparent inconsistency in how reviews resolve.

How far back a check reaches

A goal is checked back to the beginning of the attacking possession, which fixes how far a review may search for an earlier infringement. A foul several passes earlier in the same unbroken move can therefore disallow a goal, while one occurring before that possession began cannot. The rule exists to stop reviews reaching indefinitely into the past, which would make every goal provisional until the final whistle.

Where the possession began is itself a judgement, particularly in a long move containing a turnover somewhere in the middle of it. This provision is the least intuitive part of the system and the one most often mistaken for inconsistency.

The on-field review and who decides

For judgement calls the referee is invited to view the footage rather than being told an outcome, and the final decision remains entirely his. For factual matters the information is simply communicated, since there is nothing left to weigh once the fact has been established. That division preserves the principle that the referee decides, even where the information reaching him has changed considerably.

The delay it introduces is the real cost, and competitions have experimented with announcements and displays to make the process legible to spectators. Legibility rather than accuracy is where the remaining dissatisfaction with the system now tends to concentrate.