Sennett Devermont said the moment he saw flashing lights behind him after making an illegal right-on-red turn in Santa Monica, he started recording audio on his cellphone.

"In court, it’s my word against the officer’s and I believe I would lose every time," he said. "So with that audio, I was able to say to the court this is really what I sounded like, this is what I said, this is what he said."

Devermont, the mastermind behind a popular mobile app that lists local DUI checkpoints called "Mr. Checkpoint," posted the confrontation on YouTube and it received more than a million views.

That video also helped him secure a $70,000 judgment with the City of Santa Monica.

In the recording, Devermont is heard telling the officer that he has a right to refuse a field sobriety test.

"Do I have to do this?" he asked the officer.

"Yes, you do," the officer responded.

"By law?" Devermont continued.

"Yes you do," the officer repeated.

"I don’t think I do," Devermont replied.

The American Civil Liberties Union of Southern California says Devermont had a First Amendment right to refuse the field sobriety test, but adds that an officer can still make an arrest if there’s reasonable suspicion of drunken driving.

In this case, though, a judge did not believe the officer had that.

In court documents, U.S. District Judge Dean Pregerson said it is his belief that the officer was "antagonistic" and that Devermont had "simply and calmly" asserted his right not to perform any field sobriety test.

"Where the hell did you learn that from?" the officer is heard saying in the recording.

Devermont responded "That’s the law, officer."

Devermont said he had studied much about DUI law in the state of California ever since he started his Mr. Checkpoint app nearly five years ago.

"I imagine this is something that happens quite a few times but it’s not actually captured on a recording," said ACLU Staff Attorney Jessica Price.

Upon reading up on the case, Price applauded Devermont for having the foresight to start recording with his phone.

"Here, the officer said the speech was slurred and that the plaintiff was being antagonistic," she said. "But by reviewing the recording, the judge was able to make his own assessment that the plaintiff’s speech was in fact not slurred, and that if anyone was being antagonistic in this encounter, it was the officer."

Devermont spent a night in the Santa Monica jail and a blood test confirmed he had not been drinking. He filed a lawsuit against the city and it took three years before it was settled.

The ACLU said a phone can be a powerful tool. In Devermont’s case, even the judge believed the officer did not have the reasonable suspicion to arrest him and that it was “merely for retaliation” against him.

"Certainly this night the footage was worth $70,000," Devermont said, adding that he believes everyone should take the moment to record their interaction with police for any reason.

Neither the Santa Monica Police Department or anyone from the City of Santa Monica returned NBC4’s request for comment.