Sandra Bland was pulled over on July 10 for a failure to signal. But it was her decision to not put out her cigarette that resulted in her arrest. She died in prison three days later.

The question is: Did Bland break any laws by keeping her cigarette lit?

No, according to Ronald Sullivan, Jr., a clinical professor of law and director of the Criminal Justice Institute at Harvard Law School.

Texas state trooper Brian Encinia asked Bland to put out her cigarette about nine minutes into the dashboard camera video below, which was released by the Texas Department of Public Safety. When Bland refused, inquiring why she should have to put out her cigarette in her own vehicle, Encinia demanded she get out of the car. Bland once again refused, and Encinia forcibly removed her from it and arrested her. It was a series of events that, to Sullivan, appear illegal.

“Ms. Bland was in her own car and clearly old enough to lawfully smoke,” Sullivan tells BDCwire. “I am unaware of any law in any state that empowers the police to order a citizen to extinguish a cigarette when that citizen can lawfully possess and smoke a cigarette.”

The Fourth Amendment protects from unreasonable searches and seizures. Though there’s clearly no constitutional right to smoke, smoking doesn’t provide a basis under the constitution for the police to seize and search a citizen.

And Sandra Bland was indeed seized out of her vehicle. That, according to Sullivan, infringed on her Fourth Amendment rights.

Sullivan doesn’t believe that Encinia had probable cause to arrest Bland, evident, he says, in Encinia’s failure to mention their altercation over the cigarette in his official police report. This is a crucial component of this case that, without the dashboard camera, would never have been known.

“This underscores the importance of dash-cams and should also demonstrate why every jurisdiction should move to body-cams, as well,” says Sullivan. “The unblinking eye of the camera tells no lies.”