Assistant referee (association football)

The assistant referees' duties generally consist of judging when the ball has left the field of play – including which team is entitled to return the ball to play, judging when an offside offence has occurred, and advising the referee when an infringement of the Laws has occurred out of his or her view.

The fourth official will generally spend the game in the vicinity of the teams' technical areas.

The Laws also allow for designated reserve assistant referees who have no other responsibilities unless called upon to replace a member of the officiating team who is unable to continue.

During the game each assistant referee oversees one touch-line and one end of the field utilising the diagonal system of control.

The more senior of the two assistants will normally occupy the side of the field containing the technical areas, to help oversee substitutions.

In 1996, the name was changed, primarily to better reflect the modern role of these officials, and secondarily to become non-gender specific, though the term is still in widespread unofficial use.

The fourth official typically has a short distance from the touchline between the two teams' technical areas, however their positioning is not defined by the Laws of the Game.

Recent trials, for example at the 2009–10 UEFA Europa League group stage, have been started to make place for an additional two assistant referees to be added to the game, positioned behind the goal lines, to "ensure that the Laws of the Game are upheld, informing the referee of incidents of any kind that they may otherwise have missed, particularly in key areas of the field like the penalty area and its surroundings," but only informing the referee of their observations through a wireless communication system.

Their positioning also gives a good view to assist the referee in "ghost goal"-type incidents.

The trial was evaluated by International Football Association Board (IFAB) technical experts.

[4] Following a two-year experiment in the UEFA Champions League, Europa League and Euro 2012, as well as the AFC President's Cup and competitions in Brazil, France, Italy, Morocco and Qatar, the use of additional assistant referees was approved by the IFAB in July 2012.

[citation needed] The fifth official had access to television coverage of the match, but was not permitted to advise the on-field referees of any incidents they had missed.

[8] Speaking after the 2006 FIFA World Cup Final, Italy coach Marcello Lippi claimed that the referee had sent off France player Zinedine Zidane after receiving advice from "the fourth and fifth officials looking at the video at the edge of the pitch".