George Zimmerman, shown here in 2013, is not expected to face federal civil rights charges for the 2012 shooting death of Trayvon Martin. (Gary Green/AP)

The Justice Department is not expected to bring civil rights charges against George Zimmerman in the 2012 shooting death of Trayvon Martin, according to three law enforcement officials, despite allegations that the killing was racially motivated.

The federal investigation of Zimmerman was opened two years ago by the department’s civil rights division, but officials said there is insufficient evidence to bring federal charges. The investigation technically remains open, but it is all but certain the department will close it.

Investigators still want to “dot their i’s and cross their t’s,” said one official, who like others spoke on the condition of anonymity because they were not authorized to comment on the matter.

Martin, a 17-year-old African American from Florida, was unarmed when he was fatally shot by Zimmerman, a former volunteer neighborhood watchman who identifies himself as Hispanic. The killing sparked racial tension and protests across the country and drew emotional responses from President Obama and other top administration officials.

Zimmerman was acquitted of second-degree murder and manslaughter in a state trial in Sanford, Fla., last year. Even so, civil rights and African American organizations urged Attorney General Eric H. Holder Jr. to bring a federal civil rights case against him.

On Wednesday, a spokeswoman for the Justice Department said the investigation “is active and ongoing.”

An attorney for Martin’s family said his parents have not heard a final decision from U.S. officials.

“Trayvon’s parents continue to hope and pray for justice, and they won’t have any comments until they hear officially from the Justice Department,” said Benjamin Crump, who also represents the family of 18-year-old Michael Brown, whose shooting by a police officer in Ferguson, Mo., in August also prompted a public outcry.

Mark O’Mara, the lawyer who represented Zimmerman, said that approximately 40 witness statements collected by investigators in 2012 indicated there was no evidence to support a civil rights prosecution.

“I was watching the whole case pretty closely for two years, and they didn’t do anything except take those 40 statements,” O’Mara said. The statements “suggested that George acted in very non-racist ways. He took a black girl to the prom. His best buddy was a black guy. He mentored two black kids. He sought justice for a black homeless man beaten up by a white cop’s son.”

“To those who have seen civil rights investigations and civil rights violations,” he said, “it looked as though the Department of Justice was just placating pressure that existed by suggesting there was an ongoing investigation.”

The difficulty in bringing charges in the Martin case highlights the challenges for investigators in federal criminal civil rights cases. Under federal law for hate crimes, prosecutors would have to show not just that Zimmerman followed Martin because of his race but also that he shot the youth intentionally because he was African American.

A similarly high standard would apply to the case of Brown, an African American who was shot at least six times by Darren Wilson, a white police officer in Ferguson.

At a news conference last month to announce an investigation into the Ferguson police department, Holder was asked about the lingering civil rights probe into the Martin homicide.

“That investigation’s ongoing,” he told reporters. “There are active steps that we are still in the process of taking. There are witnesses who we want to speak to as a result of some recent developments.”

Two law enforcement officials said federal investigators wanted to look at a computer belonging to Zimmerman that had not been examined for the state trial in Florida.

One official with knowledge of the case said it was highly unlikely that the computer would have any evidence indicating that when Zimmerman fatally shot Martin he acted with the intent to deprive Martin of his civil rights.

Federal officials have privately said all along that a civil rights case against Zimmerman would be hard to prove.

“These are very difficult cases to make,” said one law enforcement official with knowledge of the case. “There is a high burden. We have to prove that a person was doing this with the intent of depriving someone of his civil rights.”

The investigation of the Brown shooting is being conducted under a different federal civil rights statute, the one governing official misconduct. Under that statute, it is a crime for law enforcement officers to act unreasonably and willfully to deprive a person of a constitutional right.

The Justice Department has other high-profile civil rights investigations that remain open, including one into the fatal shooting of Oscar Grant III by a Bay Area Rapid Transit police officer in Oakland, Calif., on New Year’s Day 2009.

The officer, Johannes Mehserle, was found guilty of involuntary manslaughter in 2010 but not guilty of second-degree murder and voluntary manslaughter in the shooting of Grant, who was unarmed. The case was featured in the movie “Fruitvale Station.”

Julie Tate contributed to this report.