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Sign-stealing is at the center of a new controversy. Here’s what it’s all about

MLB’s investigation concluded the Astros employee was trying to determine if the Red Sox were using dugout video monitors to steal signs from the Astros.Barry Chin/Globe Staff

Sign-stealing is at the center of a new controversy that emerged Tuesday night, involving the Red Sox and the Houston Astros.

Major League Baseball confirmed it investigated the suspicious actions of an Astros team employee at Fenway Park during Game 1 of the ALCS.

An industry source told the Globe that MLB’s investigation concluded the Astros employee was trying to determine if the Red Sox were using dugout video monitors to steal signs from the Astros.

“This isn’t sign-relaying,” the source said of the activities by the Houston employee.

Sign-stealing represents a baseball practice as old as the original act of giving signs, with information warfare serving as a baseball practice so standard that it’s reached the hallowed status of “tradition.” The effort by teams to decode information relayed from coaches to their players and from pitchers to catchers is a practice that spans baseball generations.

Here’s an explanation of the various components of sign stealing.


WHAT IS IT? Sign-stealing relates to individual or team efforts to decode the information relayed among members of an opposing team. Most frequently, teams have tried to crack the proverbial code related to the signs conveyed by:

■  a catcher to his pitcher regarding pitch type (fastball, curveball, changeup, etc.) and location (in, away, up, down);

■  a third-base coach to a batter and/or baserunner regarding a play (bunt, steal, hit-and-run, etc.);

■  an individual in the dugout (usually a manager or coach) to either the third base coach or players in the field regarding the aforementioned plays as well as defensive strategies such as pitchouts. The most common efforts relate to the game’s most common event, pitches thrown to a hitter. It’s worth noting that sign-stealing is distinct from efforts by one team to identify an opposing pitcher who tips his pitches through some sort of physical tell such as how he holds his glove or the position of his head.


HOW IS IT DONE? The most straightforward practice involves a runner on second base watching what sign a catcher puts down and flashing some kind of signal to the hitter. There have been more sophisticated techniques, perhaps most famously the 1951 Giants’ use of a telescope from their center-field clubhouse to detect signs, with the information (fastball or breaking ball) relayed to a member of the team in the bullpen, who in turn offered a signal to the hitter of whether a fastball or breaking ball was coming. The Giants went on a historic season-ending run, beating the crosstown Brooklyn Dodgers in a one-game playoff to advance to the World Series.

Tim Kurkjian of ESPN once detailed a 1980s White Sox scheme that involved flashing a refrigerator light on the scoreboard to indicate whether a fastball or breaking ball was coming; current Red Sox president of baseball operations Dave Dombrowski was a young executive for the White Sox at the time.

Over time, with the advance of technology, espionage techniques have become more sophisticated. With cameras and screens — not to mention pitch-tracking technology — now all over the park, the mechanisms for sign-stealing have increased.

In 2017, a controversy involving the Red Sox and Yankees represented a new potential wrinkle of the undertaking. In that instance, a member of the team’s staff who watches the games on a monitor to decide whether to challenge rulings on the field relayed pitch information to a trainer wearing an Apple Watch. That information was then ultimately relayed to a player.


WHAT DOES IT ACCOMPLISH? In theory, a hitter can achieve a considerable advantage if he has information about the pitch type or intended location. That said, hitters are divided on the benefit of sign-stealing. Some eschew feedback for fear of cluttering their minds — or out of terror that they might get bad information, rendering them vulnerable not just to a bad at-bat but the possibility of getting hit by a pitch.


“Sign-stealing is not an uncommon practice and there in fact is not a rule against it,” MLB commissioner Rob Manfred said in 2017.

Umpires leave it up to players to police themselves on the matter. There are instances where accusations of sign-stealing have prompted brushback pitches, threats of brushback pitches, and even physical confrontations.

But those disputes reflect interpretations of the game’s unwritten rules as opposed to codified breaches of baseball law.

IS IT WRONG? That’s an eye-of-the-beholder question. Dombrowski said in 2017 he had no beef with the practice.

“Do I think sign-stealing is wrong? No, I don’t,” he said. “I guess it depends how you do it. But no I never thought it was wrong. I guess everybody in the game has been involved with it throughout the years. People are trying to win however they can. It’s an edge they are trying to gain. Sometimes your sophistication of signs can make a difference.


“So no, I never felt like it’s wrong. Put it this way, I was never brought up that it was wrong.”

SO WHY IS THIS A BIG DEAL? While sign-stealing is not prohibited, the use of electronic devices in dugouts (save for a couple of specific exceptions that do not involve sign-stealing) is a breach of baseball’s rules. Major League Baseball clarified that stance in a preseason bulletin to teams in 2017, which defined the restricted use of electronic equipment thusly:

“The use of electronic equipment during a game is restricted. No Club shall use electronic equipment, including but not limited to walkie-talkies, cellular telephones, laptop computers or tablets, to communicate to or with any on-field personnel, including those in the dugout, bullpen, field and, during the game, the clubhouse.

“No equipment may be used for the purpose of stealing signs or conveying information designed to give a Club an advantage. Laptop computers and hand held devices are not permitted on the bench or in the dugout.

“The only exceptions to this prohibition are the use of a mobile phone for communication between the dugout and the bullpen, and the use of tablets in the dugout or bullpen running uniform programs, so long as such devices and programs have been approved by the Office of the Commissioner.”

WHAT ARE THE POTENTIAL REPERCUSSIONS? After last season’s incident, the Red Sox were fined an undisclosed amount by Manfred for improper use of an electronic device in the dugout. The Yankees were fined a lesser amount when an investigation determined they committed a similar violation prior to the 2017 season.


Alex Speier can be reached at alex.speier@globe.com. Follow him on Twitter @alexspeier. Follow Andrew Mahoney on Twitter @GlobeMahoney.