Fulton County District Attorney Paul Howard said he may ask the U.S. Attorney’s Office to investigate the 2011 police shooting death of an unarmed black teenager for possible federal charges.

Howard said he believes former Union City officer Luther Lewis committed crimes and violated the rights of Ariston Waiters by shooting the 19-year-old twice in the back as he was lying on the ground with one hand cuffed.

A federal review is the only option left after Howard’s office failed for a second time to convince a local grand jury that Lewis deserved to face criminal charges. Howard said he wants to determine whether a federal review is a possible next step to get justice.

“We want to review it and see whether or not it makes sense,” Howard told The Atlanta Journal-Constitution/Channel 2 Actions News on Friday. “If it does make sense we might ask (U.S. Attorney) John (Horn) to look at it.”

Grand jurors on Thursday declined all of the 11 potential charges that Howard's office presented, including felony murder, false imprisonment, aggravated assault and violation of oath. A grand jury in May 2012 also cleared Lewis, who gave emotional statements both times to grand jurors.

The longtime Fulton DA said the emotional statement that Lewis made after other testimony may have trumped the facts of the case. Georgia law gives police officers a special privilege to sit in on the entire grand jury proceedings when they may be charged and allows them to make a final statement. These sworn statements by officers can be full of tears and even outlandish statements about what happened or claims about witnesses that have testified in the state’s case, Howard said. But prosecutors cannot cross examine the officers or question them. He said these statements can sway grand jurors because they are the last thing they hear before they decide whether to bring charges.

Observers said Lewis was crying at several points during the two days of grand jury testimony this week and his final statement that lasted more than 90 minutes Thursday night was emotional and powerful. Grand jurors interviewed from the May 2012 grand jury that also cleared Lewis said his final statement was influential in the final decision.

“In many cases we’ve had before I believe it’s been a factor and I believe it was a factor in this case as well,” Howard said. “Emotion is generated in an unabated fashion. That is what we see…But we cannot talk about specifically what happened. What I’ve described before, I believe this case would be consistent with that.”

Howard would not discuss how jurors voted on Thursday night, and jurors were ushered out of the courthouse after their decision. Unlike criminal juries, a grand jury does not require a unanimous vote to reach a decision.

Information is not available on the racial makeup of the 23-person grand jury, but witnesses said it was a diverse group.

Lewis was unavailable for comment Friday but a group identified on a Facebook page only as “Friends of the Union City Police” lauded the grand jury’s decision.

On the night of Dec. 14, 2011, he was responding to a report of teens fighting and shots fired when he apparently saw Waiters running away from the scene and gave chase. Lewis drew his gun and ordered Waiters to the ground.

As Waiters was lying face down on the ground and being handcuffed, Lewis shot him twice in the back at close range. There were no witnesses to the shooting. Lewis claimed the teen went for his gun as he lay on the ground with one hand cuffed.

Howard reopened the case in May after the news organizations' investigation cast doubt on the official justification for Lewis pulling the trigger. At least half of the roughly dozen witnesses — some first identified by the AJC/Channel 2 — did not testify before a May 2012 grand jury that cleared Lewis.

Howard said his office called several Union City officers this week who gave testimony that could call into question Lewis’s story. He thought the historic nature of the officers breaking ranks to give testimony against a fellow officer would be powerful, along with the DNA evidence and new evidence presented regarding an earlier incident where Lewis, who is white, pulled his gun on a black motorist. But it wasn’t enough to overcome Lewis’s final statement.

“We thought it was convincing, but as I said, we always know that there’s this 800 pound gorilla waiting for us,” Howard said.

The Waiters family won a civil settlement in the case, but Freda Waiters, Ariston's mother, said she is not giving up her fight. She was at rally on Friday morning on the courthouse steps where there was talk of carrying the case to the federal level.

"It's not the end," she said. "I'm going to continue to fight for justice for my son."