MINNEAPOLIS — Lola Velazquez-Aguilu, her husband and two children were headed on a family vacation last summer when a call came.

It was Minnesota Attorney General Keith Ellison, who had just taken over the state’s prosecution of the former police officers accused of killing George Floyd. Ellison (D) wanted her to serve as a special prosecutor on the case, but she was reluctant.

A former federal prosecutor with the U.S. attorney’s office in Minnesota, Velazquez-Aguilu, 41, had spent much of the past few years tied up in grueling trials, long hours that had taken a toll at home. Her son had called her crying during her last big case because he desperately missed his mom.

“For me, the first thought was, I don’t know that I can do this to my family,” she said.

But as she ended the call with Ellison, she heard that same son call out to her from the back seat, where he had quietly been listening to the attorney general’s pitch via the car’s Bluetooth. The 11-year-old knew all about Floyd from the news and the protests that had erupted across the Twin Cities in the aftermath of his May 2020 death.

“Mom, you have to do this,” he told her. When Velazquez-Aguilu began to remind him how hard the last trial had been on him, he interrupted. “Mom, I know,” he said. “But I’ll be okay.”

Something in her son’s voice made her think of the viral video that had captured Floyd crying out for his own mother as he begged for air, and ultimately his life, with a White police officer’s knee pressed into his neck until he went limp.

Velazquez-Aguilu, who is Puerto Rican, looked back at her son — already taller than most kids his age, with his brown skin and shy personality. She often worried what might happen if he encountered a police officer who mistook his awkwardness for something else.

“It just punched me in the gut,” Velazquez-Aguilu said. “And from that moment on, in many ways, I couldn’t think about this case without thinking about my son.”

She called Ellison back and told him she’d join the case.

Former Minneapolis police officer Derek Chauvin was sentenced last month to 22½ years in prison for murder in Floyd’s death. Three other former officers are awaiting trial in the case. And while Velazquez-Aguilu never set foot in the courtroom, she is credited with playing a key role in the trial, including finding an expert witness who was crucial to the prosecution’s case: a pulmonologist who had studied and written about the mechanics of breathing.

Now, Velazquez-Aguilu is one of three finalists to be the next U.S. attorney for Minnesota, a nomination that is expected to be announced soon. If nominated by the Biden administration and confirmed by the Senate, she would be the first Hispanic person to lead the U.S. attorney’s office in the state and only the third woman. As U.S. attorney, she would oversee the federal prosecution of Chauvin and the other officers who have also been charged with violating Floyd’s civil rights.

“Despite having zero public role, she was integral to the [Chauvin] case. I mean, integral,” said Neal Katyal, a former acting U.S. solicitor general who is also serving as a special prosecutor in the case against the former officers. “She weighed in on literally everything. … Nobody got to see what she did, but it was as good a performance from a lawyer as I’ve ever seen in my life.”

As a federal prosecutor, Velazquez-Aguilu specialized in white-collar crime. She had never been involved in the prosecution of a police officer, but she brought to the case a deeply personal perspective: Her mother had been a police officer in Madison, Wis., and was the first Latina officer in the state.

Velazquez-Aguilu had grown up around police and watched her mom work the night beat. She was acutely aware of the dangers of the job and the split-second decisions that officers are often forced to make.

But she was also aware of another side of policing. Her late father, a social justice activist, had been severely beaten by New York City police when he was just 14, losing a thumb. When she was a kid, he told her and her brother to always tell police officers that their mother was a cop in hopes of diffusing any tense situations. Velazquez-Aguilu had recently given her son similar advice. “Say right away: ‘My grandma is a police officer.’”

“Because of my mom, I feel like I have a very clear view of what’s right and what’s wrong,” Velazquez-Aguilu said. “My parents talked a lot about justice and what justice means. … And I really do feel in so many ways that this kind of prosecution is in service of the police. We cannot let it stand that anybody could ever believe this is what policing entails.”

Velazquez-Aguilu, who works as an in-house counsel for a medical technology firm, was assigned the task of building the prosecution’s medical case — a crucial role given that Chauvin’s defense believed Floyd’s preexisting health issues and drug use were their client’s best chance at an acquittal.

“Causation was going to be a problem. We knew we needed to not just try to show what did kill George Floyd, but also debunk things that certainly did not kill him,” Ellison said. “And what Lola did was exceptional in every way.”

The resulting case included overwhelming video evidence of Floyd’s pain and suffering, and gripping testimony from witnesses Velazquez-Aguilu helped recruit, including Martin Tobin, a Chicago-area pulmonologist who pointed to graphic body-camera video showing Floyd’s desperate attempts to breathe and the exact moment he died.

While Ellison had hoped Velazquez-Aguilu might serve as one of the courtroom attorneys during the Chauvin trial, her responsibilities at the medical technology firm kept her behind the scenes. She spent her off hours and weekends preparing the medical case, often sleeping as little as two or three hours a night.

She watched the graphic videos of Floyd’s death again and again, looking for crucial moments — the positions of the officers on Floyd’s body; what Floyd was saying and what officers said to him; the point when Floyd’s breathing begin to slow. Hundreds of times, she listened to Floyd beg for his life and watched him die.

“It was hard,” she said. “I remember last summer I would need a break because it was traumatizing to watch over and over.”

But there was no reprieve. On walks around her South Minneapolis neighborhood, she saw Floyd’s face everywhere — on signs in neighbors’ yards and on street art demanding justice in his death. She found herself unable to sleep. “I couldn’t watch and watch and watch and then try to go to bed,” she said. “I had to put in guardrails for myself.”

Yet that meticulous analysis led to key revelations that would prove damning to Chauvin’s defense, which claimed the former officer had placed barely any weight on Floyd’s body. One day, Velazquez-Aguilu got a call from Joshua Larson, an assistant Hennepin County prosecutor, who pointed her to a video turned over in discovery showing a different vantage point of Floyd and the officers.

Together, she and Larson watched as Chauvin appeared to ride up and down on Floyd’s body as the Black man shifted on the ground, struggling for breath. It was like “those pony rides at the grocery store,” she said.

“It was that moment we realized it wasn’t just the left knee on the neck,” Velazquez-Aguilu said. “In fact, both of his knees and his full body weight were on George Floyd.”

As she watched the footage, she found herself thinking of her mother, who had often taken her and her brother to outreach events as she sought to connect with the community she policed.

“I’d be with her at the grocery store, and sometimes people who she had arrested would come up to her and say, ‘I want to thank you’ or ‘You really helped me that night,’” Velazquez-Aguilu said. “I thought about her so many times when I watched the video because it was so heartbreaking to think about what George Floyd would have experienced had a cop like my mom shown up.”

When Rosa Aguilu, who ultimately became a Madison police detective before retiring after more than 26 years on the force, learned that her daughter would be a special prosecutor in the Chauvin trial, she felt pride, but also concern. She knew her former colleagues were likely to see the prosecution as an attack on the profession.

“I felt that some people would say, ‘Oh, how could she do that? Her mom was a police officer,’” Aguilu said. “But that’s exactly why I felt she was the right person. … When you have someone who knows what good police work is, it’s going to benefit us. Because when things like this happen, it destroys a lot, and it makes the job very hard.”

One of the biggest challenges Velazquez-Aguilu faced was taking extremely technical medical evidence and making it accessible to jurors. She called her cousins, who are physicians, for advice.

“If I want to find a doctor who can make the point that LeBron James could not have sustained this, what kind of doctor is that?” she asked one cousin, a critical care doctor.

He told her she needed a doctor who studied the science of breathing. An outside firm helping prosecutors identify expert witnesses came across a textbook that Tobin, a pulmonologist and critical care doctor at Loyola University, had written about the mechanics of breathing.

“It was almost like he was waiting for us to call,” Velazquez-Aguilu said. “The first time we talked to him, I think all of us were like, ‘This is the guy.’”

Velazquez-Aguilu commended Tobin, who had testified numerous times in civil cases but never in a criminal trial, for communicating complicated technical information in a way that connected with jurors. But Ellison and other members of the prosecution credit her with helping Tobin and the other medical witnesses to make their testimony more accessible.

Not only did she help prep the witnesses, Ellison said, she also wrote long outlines for the attorneys who were in the courtroom for their direct examinations. She also led a team that created graphics and charts explaining the testimony.

But Velazquez-Aguilu didn’t limit her scope to the medical evidence. Those involved say she offered input on virtually every aspect of the case — recalling how she would readily weigh in on strategy during the team’s daily video calls, which included lawyers and advisers from across the country.

While those close to the case were limited in what they could disclose — citing Chauvin’s expected appeals and the looming trial of the other officers — Katyal said Velazquez-Aguilu, whom he had never met, was often the first to comment on drafts of briefs he had written. She offered such good advice that he ultimately never filed a brief without first getting her input.

“I’ve worked with a lot of really incredible lawyers. She’s really among the very best,” Katyal said. “She pays meticulous attention to detail. She is strategic. And most of all, she’s incredibly balanced. And you look for that, particularly in a prosecutor, because you have so much power.

“And I just found time and again, she just had a really sensible, pragmatic middle-of-the road approach that I just really admired,” Katyal said.

Velazquez-Aguilu declined to comment on the U.S. attorney search. Her name first surfaced in March along with two other finalists, former colleagues from the U.S. attorney’s office: Andrew M. Luger, who held the top job from 2014 to 2017, and Surya Saxena, a former assistant U.S. attorney who worked with Velazquez-Aguilu on white-collar crime and other cases.

The process of choosing a U.S. attorney is usually shrouded in secrecy, but it has been unusually public this year, as outside groups have pressured the Biden administration to deliver on promises to improve diversity in the nation’s criminal justice system as part of the racial reckoning that came in response to Floyd’s death.

In March, the Congressional Hispanic Caucus sent a letter to Biden urging him to pick Velazquez-Aguilu, citing her record as a federal prosecutor, her pro bono role in the Floyd case and the fact that she would be the first Latina to hold the position.

“Hispanic communities are not monolithic, and it is important to the CHC that diverse and qualified Hispanic candidates who understand these nuances be considered for administration positions,” caucus Chairman Raul Ruiz (D-Calif.) wrote in the letter.

But those who have worked with her say Velazquez-Aguilu is more than a diversity pick.

“She’s an exceptional prosecutor and would make a wonderful U.S. attorney,” said Ellison, who has championed her nomination.

On the day of the Chauvin verdict, Velazquez-Aguilu raced to the courthouse, one of the few times she met other members of the prosecution team in person. At a news conference, she stood behind Ellison, who thanked her for her work — one of the only times she was publicly credited for her role in the trial.

A few days later, she was hit by a wave of sadness, an emotion that had been pent up for months as she worked on the case. She felt anguish for the Floyd family, who had fought for justice while having to endure their grief so publicly. A guilty verdict, while historic, would never replace Floyd.

But she also felt sadness for Chauvin. “Every time I saw him, I thought, ‘I wish for your sake, you had done different,’” she said.