When a ball moves anywhere on the course (prior to 2019, or without the Local Rule under 18-2, both of which account for accidental movement on the putting green), the Rules of Golf have historically cared about what caused it to move. Was it the ball settling down in the rough due to gravity? An outside agency or influence? An opponent? The player’s caddie?

The standard has also changed a bit in recent years, and changes again from 2018 to 2019. In 2018, the standard for deciding what caused a ball to move was often considered to be the “majority” standard. Technically called the “weight of evidence” standard, it was used to decide whether a player (or an opponent) caused the player’s ball to move.

If, after considering all relevant circumstances, if the weight of the evidence indicates that it is more likely than not that he or she was the cause (Decision 18-2/0.5), then the player was deemed to have caused the ball to move. This Rule and definition requiring essentially a 51% likelihood that the player caused the ball to move was a judgment that, many felt, was a bit too penal and tough to adjudicate fairly across all players and situations. Additionally, a separate higher standard of “known or virtually certain” applied in deciding whether an outside agency caused a ball to move.

The 2019 Rules of Golf address both of these issues. In 2019, under Rule 9.2 a player is deemed to have caused his ball to move using the same “known or virtually certain” standard. This raises the bar from 51% to 95%+ likelihood, and marries the two standards for any situation in which a ball at rest may have been moved by something.

The reasons for this change are pretty simple:

  • The “weight of evidence” is difficult to properly assess. Does a player stepping a foot away cause enough of a tremor in the putting green to cause a ball to move, or was there a gust of wind? The timing and specific circumstances are difficult to parse out in the moment.
  • “Known or virtually certain” becomes the standard any time a ball at rest moves.
  • This eliminates the “middle or grey area” in situations where multiple factors may have played a role in causing a ball at rest to move. By setting the standard so high, the benefit of the doubt is given back to the player, who likely hasn’t really done much to improve his lie by moving his ball slightly. Any fairly obvious movement of a ball caused by a player will meet the “known or virtually certain” standard.

In other words, when a player causes his ball to move, it’s usually pretty obvious, and the new 2019 Rules have raised the standard for blaming the player to the tested “known or virtually certain” level.

See also: Ball Moved During Search for discussion of a new Rule covering a ball moved (even by a player or caddie) during a search.