He had just left a night club in the north Georgia town of Dalton and was making a left turn on a four-lane road in 2007 when a police officer pulled him over and charged him with making an illegal left turn.
The problem: He had turned into the outside line, not the one closest to the center line.
"I just laughed at him," said McNair.
Making a left turn sounds simple enough. But after considering a lawsuit by McNair, Georgia's Supreme Court ruled Monday the state traffic law governing left turns is so baffling that it violates the constitution. The justices struck down the law.
Their unanimous finding that the rule is "unconstitutionally vague" does not bind other states, but it could embolden other challenges. About 75 percent of states use an identical statute, according to an analysis by attorney Ben Goldberg, who filed the challenge on behalf of McNair.
At the center of the argument is rambling language that has been a part of the traffic code in Georgia and other states for decades:
"Whenever practicable, the left turn shall be made to the left of the center of the intersection and so as to leave the intersection or other location in the extreme left-hand lane lawfully available to traffic moving in the same direction as such vehicle on the roadway being entered."
Local prosecutors say the meaning is simple: Drivers making a left turn must turn into the inside lane.
"It may be somewhat less than clear to someone that doesn't read law, but it makes perfectly good sense if you stop and read it," said Whitfield County District Attorney Kermit McManus, whose office handled the case.
He said the court's "strained" interpretation of the law could become a safety issue.
But Goldberg, a public defender in Dalton, said the left-turn law is too complicated for the average motorist - let alone an attorney - to pick up on its meaning.
"It's like reading another language," said Goldberg.
Besides being cited for making an improper left turn, McNair was charged with driving under the influence and obstruction of a law enforcement officer. He spent the next four months in jail because his probation in an unrelated case was revoked due to the new charges.
A jury in March 2008 acquitted him of the more serious traffic charges, but found him guilty of making the illegal left turn. He was sentenced to 12 months probation, a $500 fine, 100 hours of community service and drug and alcohol counseling.
McNair and his attorney appealed the case after discovering the left-turn issue hadn't reached the state's top court before.
The left-turn law has been challenged with less luck in other states. An identical statute in Kansas was upheld in 1991 by that state's Court of Appeals, although it conceded the language is "not well written."
The Georgia court's unanimous ruling, penned by Presiding Justice Carol Hunstein, struck down the law on grounds it is so vague that a person of "common intelligence" is forced to guess at its meaning.
For Goldberg, it's one more step toward making the left turn a little less confusing.
"As citizens, we're all entitled to be able to understand exactly what the government mandates," he said.
McNair said the decision offers a little vindication for the traffic stop he said sent his life into a detour. He lost his car and his job at a local carpet plant while in jail, and the 29-year-old said he is still searching for steady work.
"I'm trying my best to find a job - I can't find a job nowhere," he said. "This left turn charge has really set me back."