Line Referee

Line judge is defined as a type of official responsible for determining whether the ball remains within the boundaries of the playing area, particularly in tennis and volleyball such as sports. It serves as a supporting element in the officiating system, making instantaneous decisions based on visual observation. The scope of responsibility is typically limited to the sidelines and baselines of the court. The line judge observes whether the ball has touched the line and, when necessary, communicates this observation to the chief umpire using hand signals or flags.

This role requires high levels of concentration and visual tracking ability. Observation, decision making processes and reflexive intervention are among the fundamental components of line judging. In fast-paced sports such as tennis, making an accurate decision at the exact moment the ball contacts the ground is of great importance. For this reason, line judges undergo specialized training and are certified through examinations.

Line Judging in Different Sports

Line judging has different roles and positioning arrangements depending on the sport. In tennis, there are typically six to nine line judges who position themselves according to the baseline, sidelines and service service box lines. Each referee is responsible for only one specific line and communicates their decision of “in” or “out” through hand signals or verbal calls.

In volleyball, line judges are usually positioned at each of the four corners of the court. They observe foot faults by players, whether the ball lands inside or outside the court, and service errors. They may also need to observe certain situations such as block contacts. Line judges are not decision-making authorities but assist the chief referee; however, the signals they give based on their observations can lead to the stoppage of play and a review of decisions.

AI-generated image of a line judge.

Technology and Officiating Ethics

In recent years, advances in imaging technology and tracking systems have transformed the functional role of line judging. Hawk-Eye and similar electronic observation systems allow for electronically assisted verification of line calls, especially in sports such as tennis. This situation enhances the accuracy of line judges’ decisions but can also create conflicts between technological systems and human officiating decisions.

Neutrality, attention, simultaneity and ethical responsibility are among the fundamental principles in line judging. A single wrong decision by a line judge can directly influence the outcome of a match. Therefore, both national and international federations implement standardized training programs and performance evaluations for line judges. Additionally, in some tournaments, the number of line judges is being reduced as trials are conducted to transition fully to automated systems.