Investigators for Major League Baseball have determined that the Red Sox, who are in first place in the American League East and very likely headed to the playoffs, executed a scheme to illicitly steal hand signals from opponents’ catchers in games against the second-place Yankees and other teams, according to several people briefed on the matter.
The baseball inquiry began about two weeks ago, after the Yankees’ general manager, Brian Cashman, filed a detailed complaint with the commissioner’s office that included video the Yankees shot of the Red Sox dugout during a three-game series between the two teams in Boston last month.
The Yankees, who had long been suspicious of the Red Sox’ stealing catchers’ signs in Fenway Park, contended the video showed a member of the Red Sox training staff looking at his Apple Watch in the dugout. The trainer then relayed a message to other players in the dugout, who, in turn, would signal teammates on the field about the type of pitch that was about to be thrown, according to the people familiar with the case.
Baseball investigators corroborated the Yankees’ claims based on video the commissioner’s office uses for instant replay and broadcasts, the people said. The commissioner’s office then confronted the Red Sox, who admitted that their trainers had received signals from video replay personnel and then relayed that information to Red Sox players — an operation that had been in place for at least several weeks.
The Red Sox responded in kind on Tuesday, filing a complaint against the Yankees claiming that the team uses a camera from its YES television network exclusively to steal signs during games, an assertion the Yankees denied.
It is unclear what penalties, if any, Commissioner Rob Manfred will issue against the Red Sox and whether he will order a more expansive investigation to determine the extent of the Red Sox’ sign-stealing system. It is also unclear how he will proceed with the countercomplaint.
“We will conduct a thorough investigation on both sides,” Mr. Manfred said to reporters at Fenway Park, where he was present for an unrelated event. “We’re 100 percent comfortable that it is not an ongoing issue.”
Mr. Manfred said he believed he had the power to punish teams in connection with such cheating.
“Could it happen? You know, is there the authority to do that? I think the answer to that, under the major league constitution, is yes,” he said. “Has it ever happened with this type of allegation? I think the answer is — I know the answer is no.
“And the reason for that,” he added, “is it’s just very hard to know what the actual impact on any particular game was of an alleged violation.”
Boston’s manager, John Farrell, said he was aware that the players were trying to steal signs but said that he did not know they were using electronics.
“I’m aware of the rule,” Mr. Farrell said. “Electronic devices are not to be used in the dugout. Beyond that, all I can say is it’s a league matter at this point.”
Stealing signs is believed to be particularly effective when there is a runner on second base who can both watch what hand signals the catcher is using to communicate with the pitcher and can easily relay to the batter any clues about what type of pitch may be coming. Such tactics are allowed as long as teams do not use any methods beyond their eyes. Binoculars and electronic devices are both prohibited.
In recent years, as cameras have proliferated in major league ballparks, teams have begun using the abundance of video to help them discern opponents’ signs, including the catcher’s signals to the pitcher. Some clubs have had clubhouse attendants quickly relay information to the dugout from the personnel monitoring video feeds.
But such information has to be rushed to the dugout on foot so it can be relayed to players on the field — a runner on second, the batter at the plate — while the information is still relevant. The Red Sox admitted to league investigators that they were able to significantly shorten this communications chain by using electronics. In what mimicked the rhythm of a double play, the information would rapidly go from video personnel to a trainer to the players.
As part of the inquiry, baseball investigators have interviewed the Red Sox team trainers and outfielder Chris Young, a former Yankees player. The Red Sox told league investigators that Mr. Farrell; Boston’s president for baseball operations, Dave Dombrowski; and other front-office officials were not aware of the sign-stealing operation, the people said.
In the first game of the August series in question, the Red Sox prospered the first time they put a runner on second. It occurred in the second inning, and Rafael Devers promptly hit a home run, giving the Red Sox a 2-0 lead. The Red Sox went 5 for 8 in that game when they had a man on second.
Their success when they had a runner on second in the other two games of the series was mixed: 1 for 6 in the second contest and 3 for 10 in the third.
The video provided to the commissioner’s office by the Yankees was captured during the first two games of the series and included at least three clips. In the clips, the Red Sox assistant athletic trainer, Jon Jochim, is seen looking at his Apple Watch and then passing information to outfielder Brock Holt and second baseman Dustin Pedroia, who was injured at the time but in uniform. In one instance, Pedroia is then seen passing the information to Young.
The Red Sox’ tactics will add to the longstanding rivalry with the Yankees. Outside New England, the case will be reminiscent of the Spygate controversy that erupted a decade ago when the world-beating Patriots were found to have violated N.F.L. rules by spying on opponents to gain an edge.
Mr. Manfred is in a difficult position as he decides how to discipline the team and whether to continue investigating.
In Spygate, the N.F.L. commissioner, Roger Goodell, hastily took away a first-round draft pick and fined the Patriots and their coach, Bill Belichick, before conducting a thorough investigation. When more evidence of cheating later emerged, Goodell was accused of trying to minimize the damage and protect one of the sport’s premier franchises.
In baseball, the most infamous incident involving sign stealing played out in 1951, when the New York Giants overcame a 13 ½-game deficit over the final two months of the season to catch the Brooklyn Dodgers. The Giants went on to beat the Dodgers in a playoff for the pennant.
Fifty years later, The Wall Street Journal revealed that the Giants had spies at the Polo Grounds who used a telescope to steal signs from the opposing catcher, which were then relayed to Giants players from the bullpen.
In 1997, teams accused the Mets of planting small cameras near home plate in Shea Stadium to steal signals. The Mets denied that they had used the cameras to try to do so, and the league did not take any action.
More recently, the Philadelphia Phillies faced sign-stealing accusations in 2011. Several teams logged complaints with the commissioner’s office that the team used binoculars and other unauthorized methods to steal signs. Major League Baseball never imposed sanctions on the Phillies.