“If you see a person with drugs in one hand and a firearm in the other, I think that gives you a basis for thinking that a violation of federal law has occurred, and there might also be state crimes,” said Jeffrey B. Welty, an associate professor of public law and government at the University of North Carolina at Chapel Hill.

“If it is the case, as the police have represented, that they confronted a person who had drugs and a weapon at the same time, then no, I don’t think there’s any question that that set of facts would support an investigative stop or an effort to speak further with that person,” he said.

Does North Carolina permit marijuana?

North Carolina law forbids possession of marijuana, but the police said on Saturday that the officers did not “consider Mr. Scott’s drug activity to be a priority” and approached him only after seeing the firearm. If Mr. Scott had been arrested for drug possession, the severity of the charge would have depended on the quantity of marijuana seized by the police. If he had enough for only one cigarette, the charge would have been a misdemeanor.

The police have not explained why or how they assumed, from inside their unmarked vehicle, that Mr. Scott was rolling marijuana while sitting in the driver’s seat of his own vehicle.

Did Mr. Scott have a book?

Although the police say Mr. Scott was holding a gun before he was shot, friends and family members have said that he actually had a book with him. At least one sign at the protests that swept through Charlotte last week declared, “IT WAS A BOOK.”

Chief Putney said no book was recovered from the scene.

What do we know about Officer Vinson?

Three facts seem particularly noteworthy about Officer Vinson: He is relatively new to the police force, he has a clean disciplinary history and he is, like Mr. Scott, African-American.

Officer Vinson, a member of a crime-reduction unit in the department’s metro division, was placed on administrative leave after the shooting, a standard procedure here and across the country. The police said he joined the department in 2014, and has never been disciplined.