(Montgomery County State’s Attorney’s Office.)

One moment, the hotel maid was cleaning a quiet hallway. The next, she heard screams erupt from Room 201.

“Something inside of me said, ‘Record it,’ ” she would recall.

The maid pulled out her phone, placed it near an opening at the base of the door and captured the crimes unfolding on the other side.

“Marcus, stop it!” a woman shrieked. Then sounds of pushing, slapping and more shouts: “I don’t want no part in this life!”

The two minutes and seven seconds of audio — recorded at a Radisson hotel 12 miles north of the District — proved critical for authorities in Montgomery County. They built an assault and human-trafficking case against the man inside the room, Marcus Lindsey, even as they lost track of the beaten prostitute.

(Montgomery County State’s Attorney’s Office)

This week, Lindsey was sentenced to 20 years in prison, absent testimony from the victim.

“You are a master manipulator,” Montgomery County Circuit Court Judge Nelson Rupp told Lindsey. “You’re a predator, and you’re a danger.”

The judge also advised Lindsey not to ask for a new sentence down the road. “Don’t bother with filing a motion for reconsideration,” Rupp said. “It will be denied.”

The case highlighted how criminals must contend with now-ubiquitous video- and audio-recording devices, carried by nearly everyone and mounted on more and more walls.

And the case included a debate over the term “human trafficking.”

Lindsey’s attorneys argued to Rupp that their client wasn’t guilty of the type of offenses for which the statute was intended: the forced transportation and sex enslavement of victims who often come from other countries.

“I’m not here to say that Mr. Lindsey is perfect or to say that he has an untarnished past,” attorney Sarah Bartle said. “But to say that his conduct warrants the same penalty as individuals who are importing women and children into the United States, locking them in sweatshops, taking their passports — it sort of beggars belief.”

(Montgomery County State’s Attorney’s Office)

Bartle said that Lindsey admitted to a “verbal and physical altercation” with the woman and that his crimes merited a sentence of less than 10 months.

It’s unlikely Lindsey will have to serve the full 20 years. Under Maryland parole rules, human trafficking and second-degree assault are nonviolent crimes, meaning Lindsey will become eligible for parole consideration after serving 25 percent of his sentence, or five years.

In some ways, the prostitution operation set up inside the Radisson last year is typical of how the trade has migrated from street corners to services advertised online and taking place in anonymous hotel rooms. Many customers prefer decent- to high-end locations, where they can walk in as if they’re in town for business, according to investigators.

The Radisson in Rockville, with a tidy, comfortable lobby and conference center, did nothing wrong, according to the prosecutor on the case, Montgomery Assistant State’s Attorney Tim Hagan, who called the maid a “hero” in court.

In the weeks before the assault, Hagan said, Lindsey had helped the prostitute set up advertisements on the website Backpage, booked hotel rooms for her throughout the Washington area and stayed in the rooms with her between customers.

After setting up at the Radisson in March, the woman was visited by three customers — paying rates between $80 to $150, depending on the length of their stay, police said. At some point, when she attempted to leave, Lindsey stopped her and struck her in the face, Hagan said.

Lindsey was tried before a jury in December.

The maid was Hagan’s first witness. She said one of her jobs was to clean hallway carpets — sometimes with a vacuum cleaner, sometimes with a broom, as she was doing when she heard the screams. Hagan played her recording for jurors.

The victim eventually got out of the room and made her way to the hotel lobby. A staffer there called 911 and handed the phone to the prostitute. A recording of the call also was played for jurors.

“I’m okay,” the prostitute told the 911 operator. “I just got beat in the face, but I am fine.”

The operator told her the police would be there soon.

“Thank you,” the victim said. She talked to police that night but disappeared later as the case progressed.

Lindsey took the witness stand at his trial. He offered an explanation for why he was in the hotel room and why he and the woman had a physical altercation.

Lindsey said he was staying in the room because he was expecting the birth of his second child at nearby Shady Grove Adventist Hospital. He wanted to be able to get there, according to his testimony.

He said he knew the prostitute. At some point, he testified, he asked the prostitute and a second prostitute for sex, which led to an argument.

The jury didn’t buy his explanation, returning their verdict Dec. 7.

Rupp, the judge, said Lindsey’s account was part of his broader attempts to sink the case, which included trying to keep the victim from testifying.

“Your testimony during the course of this case was shocking,” Rupp said. “The arrogance that you displayed on the witness stand, thinking that you would somehow avoid accountability by coming up with ludicrous explanations, was another effort to obstruct justice in this case.”