TRENTON -- You have the right to remain silent. But how silent?

A federal lawsuit against the New Jersey State Police filed by a Philadelphia attorney claims her civil rights were violated when she was arrested for clamming up during a traffic stop in Warren County last year.

Dashboard video footage obtained by NJ Advance Media this week reveals the two troopers at the scene said Rebecca Musarra's refusal to answer questions amounted to obstruction of justice.

But after Musarra was arrested, she claims she was released by a supervisor who said the troopers needed better training. She was never charged with a crime or issued a summons.

Legal experts told NJ Advance Media that motorists pulled over for traffic violations are required to comply with a police officer's basic commands, but don't have to say much else, thanks to constitutional protections against self-incrimination.

"It's clear that if you're driving a car you have an obligation, upon request, to provide the required documentation," said Wayne Fisher, a Rutgers University criminal justice professor and former Newark police officer. Those documents include your license, registration and insurance card.

Fisher declined to comment on the circumstances of the Warren County case. But he said it's part of basic police procedure to conduct "field interviews" to determine if a driver observed violating traffic laws is under the influence or engaged in some other form of illegal activity.

Yet, he added, "absent some reasonable suspicion, citizens are not responsible to engage in conversation with police officers," though "common sense might dictate (that you) just take a second and indicate to the officer you don't want to have any conversation."

In Musarra's case, she was pulled over by a trooper who suspected her of speeding, according to documents obtained by NJ Advance Media, but never cited her for speeding. In the video, two troopers took issue with the fact that she remained silent as they asked her multiple times if she knew why she had been pulled over.

"They wanted her to incriminate herself," said Alexander Shalom, the senior staff attorney with the American Civil Liberties Union's New Jersey chapter, after reviewing the dashboard video from the incident. "They wanted her to say, 'Yeah, I was going a little too fast'"

Shalom said obstruction of justice is considered a kind of "contempt of cop" charge -- in other words, the "things that people are often arrested for when they piss cops off."

He said that even before motorists are read their Miranda warnings, they still enjoy a basic right to remain silent. And, he added, police officers should know better.

"We require civilians to act as if they know the law," Shalom said. "We should be able to hold officers to at least as high a standard."

S.P. Sullivan may be reached at ssullivan@njadvancemedia.com. Follow him on Twitter. Find NJ.com on Facebook.