If state Sen. Paul Campbell goes to court in the new year as scheduled, authorities might have to prosecute him without key evidence: a breath test indicating he was drunk during a traffic crash.

Or the case could be doomed altogether, some experts said.

The 71-year-old Republican lawmaker, who also serves as chief executive of the Charleston County Aviation Authority, was arrested in November after his car rear-ended another on Interstate 26. Campbell insisted that his wife was behind the wheel, but a witness alleged they swapped seats after the wreck. He faces charges of driving under the influence and giving false information to police.

Before he was jailed, Campbell posed a question to a state trooper, whose dismissal of the inquiry could become the legislator’s best defense against the DUI charge.

After a breath test pegged his blood-alcohol level at 0.09 percent — just above the limit for driving — Campbell asked for a blood test. He said it would show him on the other side of the 0.08 limit.

“Can I do a blood alcohol?” he said, according to video footage.

“Well,” the trooper responded, “this is what we got.”

"I'm with you," Campbell said. "I don't think I'm that high."

Under South Carolina law, an officer’s failure to accommodate such a request prohibits using the result of the breath test in court.

Attorneys who specialize in DUI law recognize that nuances in the case — including an earlier conversation between the senator and the trooper about state funding shortages for testing equipment — could affect a judge's decision about whether to exclude the evidence.

Without test results, proving a drunken driving case becomes more difficult, said Edward Phipps, a Charleston defense lawyer and former DUI officer in Mount Pleasant.

"It's a huge mistake," Phipps said. "If someone asks for a blood test, the officer is obligated to give him assistance in getting it."

The 15th Circuit Solicitor's Office in Horry County is prosecuting the case. There, Assistant Solicitor Manuela Clayton said she had seen the video but couldn't comment on specifics. A pretrial hearing will likely sort out the problem, she said.

"It is a possible issue with the case," she said. "We plan on making the arguments and letting the judge decide."

Campbell's next court date is set for Jan. 17 in front of a magistrate in North Charleston. His attorney, Andy Savage, said he would not discuss a defense strategy until the authorities formally hand over video footage that has already been released to news media.

"We want to get this matter disposed of as quickly as possible," he said. "But we have to wait and get the evidence from the state."

Campbell has stood by his innocence on all charges.

Paul Campbell dash cam

State Sen. Paul Campbell loses his balance during a November field sobriety test on Interstate 26 that resulted in his drunken driving arrest. S.C. Highway Patrol/Provided

'What I've got'

About 8:30 p.m. Nov. 4, Campbell's Mercedes-Benz SUV ran into a Summerville woman's Jeep that had slowed for traffic near North Charleston. The woman wasn't seriously hurt. But she later told S.C. Highway Patrol Trooper Travis Methvin that she had seen the Mercedes' driver trade seats with a passenger after the collision.

The trooper reported that Campbell's wife, Vicki, did not seem drunk but that the senator smelled of alcohol. Campbell also couldn't maintain his balance. Methvin's report noted other signs of intoxication such as slurred speech.

Campbell was handcuffed. His wife was ticketed on the misdemeanor charge of giving false information to the lawman.

By the time they reached the jail, Campbell had already aired some complaints about the state's DUI procedures. As they waited the required 20-minute period before taking the breath test, he aired some more.

"Listen: The DataMaster sucks, OK?" Campbell said of the test machine.

"Well, again," the trooper said, "this is what I’ve got."

"It’s all you’ve got because it’s all we give you," the senator said, referring to the state Legislature.

Methvin had already read Campbell's rights related to DUI testing. One of them demands that police give "affirmative assistance" to suspects who ask for additional testing at their own expense.

"If they clearly say they want that test," Charleston attorney David Aylor said, "you have to take them to the hospital."

But Methvin later said they would go to a hospital only if the machine failed to get a good sample.

"I'd go with that," Campbell said. "You can take my blood any time you want to."

The breath test went on. Campbell learned the result seconds later.

"Oh," he said, "can I do it again?"

"No," the trooper said.

Campbell asked about the blood test moments later.

'Take my blood'

Even people who refuse to do the breath exam should have a "reasonable" opportunity to seek outside testing, Phipps said.

For those who actually go through with a breath test, officers must make obvious efforts to help them, the attorney said.

The law states: "Failure to provide affirmative assistance upon request to obtain additional tests bars the admissibility of the breath test result in any judicial or administrative proceeding."

In Campbell's case, no such assistance was evident. Phipps said the trooper should have inquired further about whether Campbell wanted other testing.

Blood tests can register a lower reading, he said. Denying defendants access to such favorable evidence is an error that has upended criminal cases great and small.

"It might not be absolute grounds for dismissal," Phipps said. "Some judges will just exclude the (breath) reading and go forward. But some would throw out the case for a violation of the law."

Sgt. Bob Beres of the S.C. Highway Patrol agreed that the law prescribes measures that officers must take, but he would not say whether the trooper in Campbell's case took them.

"It's spelled out word for word, and we follow that law," Beres said. "As far as this case, we can't comment on that."

A judge would have to decide whether Campbell clearly asserted the right, Aylor said.

With video evidence and testimony about his mannerisms at the crash scene, authorities still could prosecute Campbell. But his attorneys could offer other explanations for his instability, such as his age and diabetes.

For a drunken driving case in South Carolina, the situation is not a first.

Officers sometimes brush off such requests because hospitals routinely refuse to do the testing when there is no court order, attorneys said. And testing done more than two hours after a wreck — as would have been the case for Campbell — is sometimes not helpful.

"Rarely do you see a case where people say, 'Here, take my blood,'" Aylor said. "But if they do, you've got to do that."

Reach Andrew Knapp at 843-937-5414. Follow him on Twitter @offlede.

Andrew Knapp is editor of the Quick Response Team, which covers crime, courts and breaking news. He previously worked as a reporter and copy editor at Florida Today, Newsday and Bangor (Maine) Daily News. He enjoys golf, weather and fatherhood.