CHARLOTTE, N.C. — A four-hour traffic safety checkpoint resulted in one arrest for driving while impaired and more than 70 other citations overnight, according to the Charlotte-Mecklenburg Police Department. 

While many people applauded the 23 officers' efforts online, a law professor said checkpoints are not all they seem.

"While I think there are some benefits in terms of the deterrent value and in terms of taking some folks off of the street who have been drinking and driving, I think that we need to begin to think about whether the costs of these checkpoints outweigh the benefits," Wake Forest University School of Law Professor Kami Chavis said.

Chavis, a former assistant U.S. attorney, knows the checkpoints are considered constitutional, but she argued they often burden the poor with fines for non-DWI crimes.

"If it's for a seatbelt violation or a broken tail light or some things like that, someone's going to incur a fine," she said.

Even though Charlotte-Mecklenburg police sometimes refer to them as sobriety checkpoints, CMPD records showed only a fraction of the arrests and citations are for driving while impaired. 

In fact, records showed some nights officers don't make a single DWI arrest, but police said arrests are only part of the mission. Deterring impaired drivers is a proven benefit, and so is ticketing and arresting sober people for less serious crimes.

Citing the number of DWI arrests made, CMPD Maj. Mike Smathers argued checkpoints prevent crashes and save lives. He said the ultimate goal is to change drivers' behavior.

"We do find impaired drivers there," he said. "If we repeatedly were not finding impaired drivers then obviously there'd be a case to be made that that's not an appropriate strategy and we would need to pivot."

Maj. Smathers reminded the public CMPD also uses its DWI task force and public education to try to prevent impaired driving.

"(Checkpoints are) not the only tool, but they are an effective tool," he said.

Maj. Smathers said the checkpoints, held on roads where crash statistics show a need for proactive policing, help improve overall safety too, evident by the people cited or arrested for other crimes.

"We have to have a traffic safety purpose for being there," he said.

Our review of city records showed the brief intrusions of people's freedom in the name of public safety accounted for more than 900 arrests and citations over the last two years, but only 11 percent, the equivalent of 103 arrests, were for driving while impaired. 

Most of the rest were for tag and inspection violations, no license, driving with a license revoked, and other traffic crimes. While most violators broke some kind of traffic law, records showed police did also arrest or cite more than 60 people for open containers and drugs.

"We do find impaired drivers there and we do find other driver offenses there that we think have an impact on traffic safety...We know we are saving a life or preventing fatal crashes if we're able to find and detect an impaired driver at those checkpoints," Maj. Smathers said. 

"There's also a residual traffic safety impact. You may come through and be not impaired at all, but you're not wearing your seatbelt, you don't have insurance," he added.

While CMPD tracks the number of arrests at checkpoints, the agency does not track the number of drivers its officers stop, which leaves attorney Bill Powers, a past member of the Governor's DWI Task Force, questioning their effectiveness.

"I think there are things that may work better. The question is how do define working?" Powers said. "I'm more of a fan of saturation patrols, because it requires police officers to be suspicious of some behavior."

Patrols require reasonable suspicion before someone's pulled over. That's not needed at checkpoints.

"They're a bit antiquated in my mind," Powers said.

CMPD routinely partners with other agencies to hold checkpoints. 

Maj. Smathers argued checkpoints don't burden the poor.

"I would disagree with that on its face," he said.

Maj. Smathers said police have a duty to enforce the law if they witness a crime. However, he told us officers do give people warnings for non-DWI crimes at checkpoints.

"The officers have discretion. We want them to use that discretion," he said. "I know they get a warning, sometimes verbal warning, sometimes warning tickets."