William “Rick” Singer ran a tight operation.

For years, he and his team churned out the bribes and lies at the heart of his college admissions scam without getting caught.

But there were close calls.

Well before federal investigators caught a break last year that led them to the Newport Beach businessman and what prosecutors allege was his network of wealthy parents and corrupt college officials, there were a handful of people along the way who caught glimpses of the deception Singer was peddling and raised red flags.

Questions from a counselor at a Los Angeles private school about a student who had been admitted to USC as a water polo player despite not playing the sport sent Singer and a USC administrator scrambling to shut down the inquiry with more lies.

And in another case, when a loose-lipped father started boasting to parents about Singer, another father paying Singer quickly told him to keep quiet.

These and other near-misses that Singer dodged underscore not just the brazenness of his operation, but the fine line he walked exploiting vulnerabilities in the opaque college admissions process and parents’ desperation to see their kids admitted into top-tier universities.

Singer largely was able to walk that line without worry, spinning subpar students into desirable applicants through over-the-top fabrications that could have been exposed if anyone bothered to check their resumes.

“This process was set up to be exploited by unscrupulous people,” said Rick Eckstein, a sociology professor at Villanova University and an expert on the high-school-to-college athletic pipeline.

When FBI agents did catch up with him in September, Singer, 58, flipped quickly, agreeing to help ensnare parents and the coaches at USC, Stanford, UCLA and elsewhere who allegedly participated in his scam. In all, prosecutors announced charges against 50 people when they unveiled the case this week and indicated more indictments could be coming.

Singer pleaded guilty to a slew of federal charges. In admitting his guilt, he laid out to a judge how since 2011 he had collected more than $25 million in a two-pronged scheme in which parents paid to have an expert test-taker on Singer’s payroll take their children’s college admission exams or to buy spots that colleges reserve for athletes.

A 200-page affidavit filed in court by an FBI agent in the case spells out the ease with which Singer, the coaches, and parents maneuvered most kids into the universities of their choosing.

But the document also details the times when things nearly unraveled.

In 2017, Devin Sloane, an executive at a Los Angeles water treatment company, went to Singer for help getting his son into USC. The affidavit shows Singer obliged, charging Sloane $250,000 to concoct a bogus athletic resume for the boy. The teen, who didn’t play water polo, on paper became a member of the “Italian Junior National Team,” and Singer attached staged photos Sloane had taken of his son pretending to play the sport.

An administrator in the school’s athletic department working with Singer then awarded the boy one of the coveted spots USC sets aside for athletes.

The plan was going off without a hitch until a counselor at the Buckley School in Sherman Oaks, where Sloane’s son was a student, contacted USC officials and asked how the student had been admitted as a water polo player, according to the court documents.

“The more I think about this, it is outrageous!” Sloane wrote in an email to Singer contained in court records. “They have no business or legal right ... to be calling and challenging/question [my son’s] application.”

Donna Heinel, the administrator working with Singer, wasted no time putting an end to the counselor’s queries. Doubling down on the lies she and Singer had made up, she sent an email to the head of the school’s admission office detailing the countries in Europe where the boy played tournaments during the summer.

“He is small but he has a long torso but short strong legs plus he is fast which helps him win the draws to start play after goals are scored,” she wrote.

Singer also sent Sloane a long script to follow in case anyone else at the school raised questions.

Years earlier, Toby MacFarlane, an insurance executive from Del Mar, had paid to get his daughter into USC as a fictional soccer player.

A member of the USC athletic department emailed the girl to alert her that a class she had signed up to take conflicted with the soccer team’s schedule of games.

The school’s soccer coach Singer had bribed had been replaced, and the new coach was perplexed when he was copied on the email.

“I don’t know who she is,” he wrote to higher-ups in an email seeking an explanation.

Singer’s fix was simple: He advised MacFarlane to explain to USC officials that his daughter had suffered a foot injury before enrolling and would not be playing.

And both times that actress Lori Loughlin and her fashion designer husband, J. Mossimo Giannulli, paid Singer to sneak their two daughters into USC as members of the crew team, counselors at Marymount High School were dubious.

Giannulli confronted the counselor asking questions about his younger daughter last year, the affidavit shows. The counselor later emailed to assure him, “I also shared with [the USC senior assistant director of admission] that you had visited this morning and affirmed for me that [your younger daughter] is truly a coxswain,” referring to a crew position.

The encounter prompted Heinel to call Singer and warn him that he needed to better prepare parents for school officials’ questions.

“Yelling at counselors,” she wrote, would “shut everything — that’ll shut everything down.”

The parents accused of involvement could not be reached for comment.

Singer boasted to parents that he had built a “side door” into USC, Yale, Stanford and other highly sought after schools.

To convince admissions committees that the students they were ushering in through the door were talented athletes, Singer, Heinel and the coaches taking bribes brazenly claimed the students were award-winning members of championship teams or earned other accolades that could have easily been detected with a simple internet search. Singer claimed one would-be basketball player was over 6 feet tall, when in fact he stood 5-feet-5.

It is not surprising that Singer rarely ran into problems, said Anthony Ashton, a Baltimore attorney and former teacher and guidance counselor.

Top-tier private schools are under intense pressure to secure their graduates coveted spots at top universities, both to appease parents who’ve been paying five-figure tuition and to bolster the school’s profile, Ashton said.

That gives counselors little incentive to go looking for signs of a scam like the one Singer was running.

“You’ve got people paying the equivalent of college tuition for 13 years,” he said. “If you’re going to ask for that kind of money, you’re going to need that pot of gold at the end of the rainbow.”

And though officials at several of the universities Singer exploited have responded to the scandal by saying they were victimized by a mastermind bent on smuggling kids past their defenses, experts said there are not many defenses to begin with.

Eckstein said that while universities typically have monitors on staff who can sit in on meetings when admissions decisions are made, it is unreasonable to expect such monitors to be able to effectively patrol all aspects of the admissions process.

They have “the potential to provide real oversight,” Eckstein said. “My guess is they just haven’t been checking whether every pole vaulter has actually held a pole.”

Especially with sports like water polo and sailing, which don’t generate much revenue or attention for a university, admissions committees will generally accept a coach’s recommendation at face value, Eckstein said. He pointed out that none of the students Singer disguised as athletes were awarded athletic scholarships.

“When there’s no scholarships involved, there’s no real downside to having a lot of kids on the roster,” he said.

Admissions committees are unlikely to double-check that recruits are who their coaches make them out to be, he added: “The only incentive to do it, really, is honesty.”