In the last decade, at least 19 NFL franchises took precautions against the Patriots that they didn't take against any other opponent.

Late last January, with Tom Brady under siege, Bill Belichick playing physicist, Robert Kraft going rogue and the country debating a strange controversy known as Deflategate, the Seahawks arrived in Arizona for Super Bowl XLIX. They were not too concerned with the Patriots’ latest “-gate.” But they had been warned about the potential for another one.

Multiple teams called Seattle, unsolicited, with advice on how to secure the team’s practices for the Super Bowl. Their message was clear: You’re not playing John Fox’s Broncos again. You’re facing Bill Belichick and the Patriots. You never know who might be watching.

The Seahawks trained in Tempe, on Arizona State’s outdoor practice fields, which left a large perimeter to secure. They worked hard to secure it. They hired extra guards and scanned any area nearby with a vantage point of the field. Security personnel monitored what locals call “A” Mountain, the 1,400-foot hill that towers above the university’s athletic complex. They combed the parking garage and parking lots between Sun Devil Stadium and the practice fields. And they checked around the boundary of the complex, where baseball and softball fields and various buildings provided clear views of Seattle’s Super Bowl drills. Several observers who have attended practices for other Super Bowls noted the unusual, Secret Service–like level of activity.

The Seahawks didn’t discover any covert operations. Most of the time New England’s opponents don’t.

But they almost always look.

Matt York/AP

At various times over the last decade, at least 19 NFL franchises took precautions against the Patriots that they didn’t take against any other opponent, people who worked for those teams told SI. Those concerns have not waned in the eight years that have passed since the Spygate scandal. The list of safeguards is long and varied. Teams commonly clear out trash cans in their hotel meeting rooms in New England because they believe the Patriots go through them. One longtime head coach said he ran fake plays in his Saturday walkthroughs at Gillette Stadium because he thought the Patriots might be spying on his team. Another team has taken things further: It fled Gillette and found a different place to practice, and on game day it piled trunks of equipment against the double doors in the back of the visitors’ locker room so nobody could get in. That same team kicked the visiting locker room manager out of the office he occupies near the clubhouse.

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In September 2007 the Patriots were found to have illegally videotaped Jets coaches during a game, something opposing teams had caught them doing at least twice previously. The NFL fined Belichick $500,000, the organization $250,000 and took away a first-round draft choice—and long-held suspicions about the Patriots cheating under Belichick were legitimized. Whispers about their activities became a year-round conversation throughout the NFL. Belichick’s coaching brilliance has never been in dispute—his ability to prepare and adapt are legendary. But he is not trusted. Even in a league filled with coaches who cover their mouths with call sheets and guard injury reports like nuclear codes, many teams view the Patriots as willing to cross lines others won’t.

You could say the rest of the NFL is paranoid, and you might be right. What’s not debatable is that New England, because of that lack of trust, is inside opponents’ heads, forcing other teams to devote time, brainpower and resources to protecting themselves. Teams wonder why ball boys in Foxborough seem to stand closer to opposing coaches than they do anywhere else. It is common for opposing teams to have an employee guard their locker room all day when they visit Foxborough, something they rarely do for other road games. One team that played there in recent years put a padlock on the doors when it arrived on the Saturday before a game. The Patriots threatened to call the fire chief. When the visiting team challenged them to do it, the Pats backed down and the padlock remained. “There has never been a time when we have knowingly allowed a team to padlock doors,” says Patriots spokesman Stacey James. “That’s a fire code violation.”

Some of the security measures are small. It is standard NFL practice for home teams to help unload equipment from buses, but one AFC team won’t let the Patriots do it. Other precautions are extreme: At least five teams have swept their hotels, locker rooms or coaches’ booths in New England for listening devices, sometimes hiring outside professionals. None have been found.

And while the Pats insist Spygate is ancient history, other teams aren’t so sure. During one Patriots road game last season their opponent suspected a man was illegally videotaping them with an iPhone from the visiting sideline. The man wasn’t wearing New England team gear, but the people who were filming during Spygate often weren’t wearing team gear either. It felt too much like Spygate II for the home team’s liking, and the man was kicked out of the stadium. James says the team is unaware of any such incident and is sure “it never happened with a Patriots employee.”

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The rest of the league has been on high alert in other ways too. The NFL has changed several rules over the last decade in response to issues raised about the Patriots or to close rule-book loopholes exploited by them, according to three people familiar with the competition committee’s decisions. In 2007, after the Patriots were accused of manipulating coach-to-quarterback radio systems and game clocks, the league mandated neutral operators for both in playoff games. After the Ravens complained about New England’s deployment of ineligible receivers in a playoff game last January, the NFL declared that in the future a formation the Patriots used will be illegal. (The Patriots say they confirmed the legality of the formation with the league before the Ravens game.) “[The Pats] were mentioned [in competition committee meetings] way more than anybody else,” one source familiar with the committee’s discussions in recent years said.

“All this stuff speaks to manifestations of the same thing,” says one NFL personnel executive. “It’s the Patriots, and it’s everybody else.”

Michael Dwyer/AP

These suspicions may help explain why NFL commissioner Roger Goodell was so determined to investigate the Patriots for Deflategate. SI spoke with dozens of people throughout pro football: team presidents, general managers, head coaches, assistants and players; some are still in prominent positions and others no longer work in the league. While they were mostly reluctant to talk on the record, most believe the Patriots have played fast and loose with league rules for years—breaking them or looking for ways around them—and they want to see the organization held responsible.

In some cases there is no rule explicitly banning the alleged actions. One example: Another AFC team has brought its own sports drinks because the ones the Patriots supply are often late, warm or both. Unethical? Or just gamesmanship? “They’ve created a culture where that type of behavior is encouraged and rewarded,” one team executive says. “Everybody there is supposed to make the visitor uncomfortable—do everything that is borderline against the rules, but clearly against the principles of good sportsmanship.”

Incidents that might be considered innocent snafus elsewhere are viewed more skeptically in Foxborough. Headset failures are not uncommon around the league—Sun Life Stadium in Miami, for instance, is notorious for frequency issues. But representatives from several teams told SI they have experienced problems with the coaches’ equipment at Gillette—echoing a complaint from the Jaguars after their 2006 playoff loss there, when coach Jack Del Rio said his team’s headsets “mysteriously malfunctioned” for most of the first half. In May, Browns linebacker Karlos Dansby told ProFootballTalk.com that his on-field headset stopped working when his Cardinals played the Patriots in 2008, and he does not think it was an accident: “They gonna do what they gotta do to win. It’s just how they operate.”

Home teams are supposed to provide certain communications equipment, but opponents often don’t trust the Patriots to do it. One team griped to SI that New England supplied a corroded battery pack. Another current head coach brings his own equipment because he doesn’t trust the Patriots to supply anything of quality. A representative of a third team says the Pats provided headset gear that looked “like it had been run over by a lawn mower. Frayed wires, the speaker is all chopped up. . . .” James says that it is league policy for all headset batteries to be changed 30 minutes before a game, and that the team has “always complied with that.” He adds, “We’ve never been cited by the league for doing anything wrong as it pertains to communication device violations.”

Another team executive says, “Anybody who has gone in there in the last five years will tell you some sort of problem or snag they never hit any other place. They are the worst hosts in football.”

Bill Belichick learned to study football long before he coached it, at the foot of his father, Steve, an assistant coach at Navy. Steve Belichick was greatly respected for his ability to prepare for an opponent. In 1962 he wrote a book called Football Scouting Methods, detailing all the ways a scout can ready his team. “It must be remembered that the primary objective of scouting is to gather as much pertinent information as you can,” Steve wrote. “In order to do this, you must carefully observe and record what the opposition does.”

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From Steve, Bill learned that if you take away an opponent’s strength, you will probably win. His ability to do that, along with Brady’s sustained excellence, have separated the Patriots from the rest of the NFL. And in Belichick’s world, no detail is too small, no idea too radical. “They do the best job, week in and week out, of coaching all the little things that make a difference in winning and losing,” says Hall of Fame executive Bill Polian, who built the Peyton Manning–led Colts teams that were the Pats’ chief rivals through the 2000s. “There is no question in my mind about that.”

Admirers and critics agree: Belichick will walk 10 miles to gain an inch on his opponent. For example, every Friday teams must announce which injured players are doubtful, questionable or probable to play that Sunday. Teams usually take 53 players to the game and announce, 90 minutes before kickoff, which seven are inactive. In 2005 the NFL began requiring visiting teams to tell opponents and local media which players were not traveling to a given game, making it clear who would be out. But before that, according to a source familiar with the Patriots' meetings in the early 2000s, Belichick would tell his staff which opposing players were not on the plane. It wasn't clear how Belichick knew. But he did. (Editor's note: This story was updated to account for the implementation of that NFL rule.)

This gave the Patriots a few extra hours to adjust to any roster changes. There was no rule against this, though some would argue that it was unseemly. Others wonder how much of an advantage such knowledge really provided. But it was quintessential Belichick.

In the popular retelling of Spygate, Jets coach Eric Mangini, a former Belichick assistant, ratted out his ex-boss. In reality, Mangini called Belichick before their September 2007 game to warn him not to film New York’s signals. And by that point the league was already eyeing the Patriots.

In 2006, after several teams—including the Giants, who caught the Patriots videotaping coaches’ signals in a preseason game that year—complained to the league about New England’s video espionage, NFL senior vice president for football operations Ray Anderson issued a memo reminding teams that “video taping of any type, including but not limited to taping of an opponent’s offensive or defensive signals, is prohibited on the sidelines, in the coaches’ booth, in the locker room, or at any other locations accessible to club staff members during the game.”

Two months later Packers security in Green Bay noticed a man filming with a small handheld camera on the sideline. When the man was confronted, he said the Patriots coaches wanted him to capture field conditions. In the second quarter security saw him apparently filming signals from a tunnel in an end zone corner and stopped him again.

During the game one former Packers staffer says, the Patriots seemed to know Green Bay’s defensive calls from the outset. The Patriots won 35–0. “Whatever we called, they got us out of our base call every single play,” the staffer says. “I’ve never seen anybody be able to do that before.”

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According to a league source, the NFL recirculated Anderson’s memo before the 2007 season. Given the memo’s existence and all those suspicions and complaints, why did Belichick continue to defy the video rule? Why did he put his franchise in position to be disciplined and disgraced? Perhaps he didn’t anticipate severe sanctions—aside from saying he “misinterpreted” the rule, the coach has never explained himself. Certainly the advantage he stood to gain is significant. Trying to figure out signals with the naked eye is legal, and most teams try it. Doing it with video cameras is illegal because a team can rewind the tape and match signals with play calls. As a longtime NFL head coach tells SI, “If a good quarterback has that information, he can really use it. It’s way, way, way important.”

One person who knows Belichick well says he does not consider the coach “a cheat.” But he acknowledges that, while others might simply obey a rule, Belichick will search for loopholes and gray areas to exploit—he’ll “study it and take it to the nth degree.

“This guy is two steps ahead of everybody because he is so brilliant. If you’re going to walk the line, every once in a while you’re stepping over. Sometimes somebody has to pull him back in. In his mind, he thinks: I’ll get an advantage and somebody else can figure out if it’s illegal. My job is to coach a football team.”

The effects of Spygate are still rippling through the NFL. In the wake of the scandal Goodell asked for two changes to league operations to help him deal with integrity-of-the-game issues. First, he demanded that every coach and general manager in the league sign an affidavit each year affirming that they did not cheat and were not aware of any cheating by their employees. Teams submit those forms at the end of the league year in March. Even a coach fired at the end of the regular season must sign the affidavit for his former team.

Goodell used those affidavits to slam the Saints in 2012 for their bounty scandal. When he famously told New Orleans general manager Mickey Loomis and coach Sean Payton that “ignorance is not an excuse,” this was not empty rhetoric. The affidavits make that the official policy.

Goodell’s second request after Spygate was to lower the burden of proof required of the league when handing down punishment in integrity-of-the-game cases. The old standard was “clear and convincing evidence.” The NFL switched the language in its Integrity of the Game policy to the less rigorous standard of “preponderance of evidence.” In the legal world that means there is more than a 50% chance that something occurred. In other words, more probable than not—the key phrase in the Wells Report that Goodell used to justify his Deflategate crackdown.

The league had engineered its code of conduct to make it easier to convict and punish the next perpetrator of a Spygate. It had also created a climate in which it was safe to make public accusations against the Patriots—no hard evidence needed. Former Rams star Marshall Faulk openly wondered in 2013 if the Patriots illegally scouted the Rams before upsetting them in Super Bowl XXXVI in ’02. The Boston Herald had reported in ’08 that the Patriots illegally recorded the Rams’ walkthrough, but the Herald retracted its report, and nobody has proved it to be true.

Of course, since Spygate other organizations have been caught breaking rules. Earlier this year Goodell suspended Falcons president Rich McKay from the NFL competition committee, fined the team $350,000 and docked it a fifth-round pick because it had piped in artificial crowd noise during home games in 2013 and ’14. And last March the commissioner suspended Browns general manager Ray Farmer for four games and fined the team $250,000 for the GM’s texting coaches during a game.

But while the Falcons and Farmer took full responsibility, the Patriots never really have—which makes it easy for opponents, rightly or wrongly, to view other teams’ transgressions as isolated incidents and New England’s as part of a pattern. Sometimes other franchises’ missteps reflect poorly on New England. In 2010 the Broncos were caught filming a 49ers walkthrough in London. Denver’s coach at the time was Josh McDaniels, the Patriots’ offensive coordinator from ’06 to ’08. The Broncos’ video operations director, Steve Scarnecchia, had worked from ’01 to ’05 as a video assistant for New England, where his father, Dante, was a longtime offensive line coach.

McDaniels claimed he never watched the tape, but he also didn’t turn in Scarnecchia to the league. The NFL fined McDaniels and the team $50,000 each, and McDaniels and Scarnecchia were fired shortly after. In 2012, McDaniels returned to the Patriots and has been their offensive coordinator since.

Belichick rarely speaks about Spygate. But last January, as he vehemently defended his organization against the ball-deflating allegations, he broke his silence on the matter. “Look, that’s a whole ’nother discussion but, the guy’s giving signals out in front of 80,000 people, O.K.?” Belichick said then. “Like there were a lot of other teams doing at that time . . . forget about that. Everybody sees our guy in front of 80,000 people. There he is.

“It was wrong, we were disciplined for it. That’s it. We never did it again. We’re never going to do it again. And anything else that’s close, we’re not going to do either. . . . Anything that’s even remotely close, we’re on the side of caution.”

Spygate spawned unprecedented sanctions and an inquiry by then Senator Arlen Specter. But the NFL’s probe did not get very far. “No one ever knew exactly what was done,” one former team executive tells SI. Even staffers who were involved in Spygate didn’t fully understand its purpose. As former Patriots videographer Matt Walsh told the The New York Times in 2008, “They just told me to film the signals, pass the tape along to Ernie Adams.”

Adams, the Patriots’ Football Research Director, is Belichick’s closest adviser. He doesn’t coach, but he has his own direct phone line to Belichick during games, and his reclusive nature, nebulous job title and role in Spygate have led people around the league to speculate on what else he is up to. Even longtime Patriots employees are not sure exactly what he does.

In the post-Spygate NFL, it’s easy for the Patriots’ opponents to see—or imagine they see—planning in random events and conspiracy in coincidences. “I just know that every time we went up there, there was always something at our hotel,” says former linebacker Bart Scott. “It was always stuff like that with New England. You knew what you were going to get with them.”

You will get uncomfortable. You will get suspicious.

You will also get hit by one of the great winning machines in American sports history—four Super Bowl titles and the league’s best winning percentage (.759) since Brady took over as the starting QB in 2001. “You play the Patriots, and they know almost everything you’re doing and every defense that you’re in,” says Chris Harris Jr., the Broncos cornerback. “Which is crazy.”

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But not necessarily duplicitous. Polian says thinking the Patriots win simply because “there is skullduggery involved is foolish.” And even New England’s harshest critics agree: The Patriots would win even if they always followed every rule. Belichick and Brady are too good. Some in the NFL hoped (and maybe even believed) that after Spygate the Patriots’ house would crumble. But Belichick’s winning percentage is actually higher since 2007 (.781) than it was before (.670). To some opponents every victory and superlative feeds the idea that the Patriots are aided by black arts.

Take New England’s aversion to fumbles over the last decade, which has drawn scrutiny since Deflategate. In Brady’s first five years as a starter (2001 to ’05) the Patriots ranked 14th in the league in total fumbles. But since ’06, when a rule change took effect allowing road teams to provide their own balls on offense—previously home teams provided all game balls—the Patriots have fumbled less than all but one other team in the NFL. Especially interesting to suspicious opponents is the way New England’s fumble rate on the road dropped when it was able to control its own game balls. While their fumble rate at home stayed fairly constant after the rule change, since ’06 the Patriots have the fewest fumbles on the road after ranking 16th from ’01 to ’05.

Is it proof that the Patriots have a history of bettering their grip by deflating balls? Of course not—but it’s more than enough to fuel conspiracy theories. One team executive says that before his team played the Patriots last season, “we looked into [their] fumble ratio. . . . Their backs don’t fumble the ball. People say, Well, [deflation] doesn’t really matter. I can tell you that if the ball is softer, it makes all the difference in the world.”

Whether you consider the Patriots cheaters depends on your vantage point. The league says they have been caught twice. To some, that’s the answer. Others say that the urban legends far outnumber the actual violations. Former NFL running back Thomas Jones, who played for five teams, says the Pats stand alone in regard to the measures they take in order to win games, “hands down,” adding “I’d say like 75% of it is sour grapes.”

Those who say the Patriots are totally innocent ignore the facts. Those who say the Patriots cheat at every turn are likely paranoid. But opponents don’t trust the Patriots to play fair, and they say they have good reasons not to. What’s not in doubt is that the Patriots have won far more than any other team in this era, and the obsession with what they may or may not be doing is as much a part of their mystique as Belichick’s game-planning or Brady’s coolness in the pocket. One league source says the suspicions help the Patriots because teams are spooked and distracted: “If the plane is late, they’re going to accuse [Belichick] of air-traffic control. It’s always going to be billed as this deliberate thing.”

Belichick is 63. The rumors and whispers will follow him to Canton someday, as will a legion of admirers. In the meantime the Hooded One tells his own staffers, Watch what you leave in hotel trash cans. Be careful whom you trust. When the Patriots played the Panthers in the 2004 Super Bowl, Belichick successfully lobbied to practice indoors on Friday, rather than outdoors at Rice, because he was concerned about spies.

He has built a Hall of Fame career on having more information than his opponent and knowing how to use it. And those who know him best understand that. Nick Saban was Belichick’s defensive coordinator in Cleveland. When Saban left Louisiana State for the Dolphins in 2005, he insisted that his defense change its signals before playing the Patriots. “They’ll get them,” Saban said, according to one staffer.

In Saban’s second year Miami upset New England. In the locker room afterward two Dolphins players said they benefited from inside information: Their team had purchased audio of Brady’s signal-calling, and it helped them figure out what play was coming.

Saban dismissed the story, saying his team has simply studied TV replays of Brady. When reporters asked Belichick about it the next day, the game’s most creative competitor laughed.

“Technology, that’s not really my thing,” Belichick said, nine months before his team’s illegal videotaping system would be exposed. “I can barely turn the computer on and off.”