ATLANTA — A former Union City police officer, twice cleared of shooting and killing an unarmed teen, is now under investigation once again, after another department fired him for lying.
Channel 2 Action News and the Atlanta Journal-Constitution have confirmed that Georgia's Peace Officer Standards and Training Council (POST), which certifies the state's police officers, is investigating Officer Luther Lewis.
"If you can't tell the truth with a badge on your chest, why should you need to be a law enforcement officer?" said POST Director Ken Vance.
[READ: Teen shot, killed by Union City police]
Vance added that lying is deemed to be one of the worst offenses an officer can commit.
"If you lie on a public document or in an investigation or on the stand, your credibility is gone from then on," Vance said.
Records show the Savannah Airport Commission hired Lewis on July 13. He worked patrolling at the Savannah Hilton Head International Airport for one week and then was terminated on July 20.
His termination letter cited "deception during the interview process."
A representative told Channel 2 Action News that Lewis never disclosed anything about his shooting of an unarmed teenager while working for Union City.
[READ: U.S. attorney looking into police shooting of unarmed man]
In 2011, Lewis chased Ariston Waiters after arriving to break up a neighborhood fight Waters was watching.
The 19-year-old was already lying face down on the ground with one arm handcuffed when Lewis shot him twice in the back.
In May, a Channel2 Action News/Atlanta Journal-Constitution investigation raised new questions about the case, prompting the Fulton County District Attorney to reopen it.
Those questions included two prior incidents where fellow officers said Lewis lied, once by saying he fired shots, because someone had shot at him, and again when he burst into an empty house while looking for a suspect.
"This allows us to look at it all," Vance said. "Lying is a character flaw. And it's a serious character flaw when you wear a badge, and you have the say so of some person's liberty."
[READ: Deadly police shooting of unarmed teen reopened after Channel 2 investigation]
The Savannah agency Googled Lewis and learned of his history and the newly reopened investigation, which prompted the firing. POST was notified just two weeks prior to the Fulton County grand jury proceeding.
Fulton County District Attorney Paul Howard told Channel 2 Action News that no one in his office was aware of the Savannah termination when prosecutors asked a grand jury to indict Lewis for Waiters' murder in early August; Lewis' statement to the grand jury was key, since it was only his word, saying the teen tried to grab his gun. The grand jury opted not to indict Lewis on any charges.
Howard asked for copies of the Savannah records to compare with what Lewis said in his grand jury statement.
"When those officers testify before a grand jury, they can say all kinds of things that are not true. And the DA's, we have no power to overturn and to cross-examine them about what they are saying," said Howard.
Vance says POST could revoke Lewis' police certification, or even charge him criminally, since he signed that his government application was completely truthful.
"Are you asking me if I would hire this person if I was a law enforcement chief? Hell no, pure and simple. If you'll lie to me once, you'll lie to me again," Vance said.