Alexander Landau was shocked that the Justice Department opted not to charge three Denver police officers with civil-rights violations in his 2009 beating case. But Friday’s news didn’t surprise experts at all.

Taking police officers to court is a tough call for prosecutors, who must prove charges beyond a reasonable doubt in the face of politics, polarized perceptions of police and evidence that different people view differently.

Proving officers violated someone’s civil rights is even more challenging because “they have to show not just overreaching and callousness, but did they mean to deprive someone of their civil rights?” said Eugene O’Donnell, a former police officer and prosecutor who is now a professor at the John Jay College of Criminal Justice in New York.

“People will be viscerally outraged, but prosecutors learn and know that the visceral outrage often will not see them through to a guilty verdict,” O’Donnell said.

With the Justice Department’s decision not to prosecute — and having already reached a $795,000 settlement with the city in a federal lawsuit — Landau and his supporters said Saturday that Manager of Public Safety Alex Martinez’s pending discipline decision is essentially their last hope that the officers will be punished.

Landau’s lawsuit said that Cpl. Randy Murr and Officers Ricky Nixon and Tiffany Middleton tried to cover up the Jan. 19, 2009, beating that left him scarred and suffering neurological damage. He said the officers hit him with their fists, flashlights and a radio and called him a racial epithet during the incident that started as a traffic stop.

Police, however, said Landau had reached for Middleton’s gun.

The Police Department’s internal-affairs bureau has completed its own investigation into the allegations, but leaders were awaiting the results of the Justice Department’s probe before making a discipline decision.

Martinez said after a previously scheduled community meeting Saturday that he hoped to obtain information from the federal agency about its investigation “that may or may not add to the view we currently have of the situation.”

He would not elaborate or offer a time for when he might issue his order.

Mu Son Chi, racial-justice and civil-rights director for the Colorado Progressive Coalition, said there is no reason to wait.

“These are different processes for different purposes,” he said.

Chief Robert White declined to comment, as did Mayor Michael Hancock, who said he had been notified of the decision but had not had a chance to read it. Both were at the community meeting, which was not related to the Landau case.

The Justice Department did not respond to requests for comment.

The decision not to prosecute has made many in the community feel that civil lawsuits are their only recourse when they believe police have violated their rights, said Landau’s attorney, Anna Holland Edwards.

“The public cannot rely on government prosecutors or internal audits to end these types of government abuses,” she wrote in an e-mail Saturday. “Citizens must continue to demand that their elected representatives act and take their cases to court where juries can decide whether this kind of conduct is acceptable.”

Cases against on-duty officers are easier to prove in civil court, where the standards of proof are lower, said Karen Steinhauser, former chief deputy district attorney in Denver who now has a criminal-defense practice.

“Police cases are just difficult to prove,” she said. “Though jurors are instructed to look at every witness the same, we tend to look at law enforcement officers as being just that: officers who enforce the law and not break it. There’s still a tendency of most people to look at officers and say, ‘I can’t believe they would do something like that.’ It’s the intangible that comes into play as far as proving these cases.”

Sometimes the only witnesses are other officers, who are reluctant to testify against their own. And while evidence alone should determine whether charges are filed, O’Donnell said cases also rise and fall on a victim’s credibility, officers’ disciplinary records, politics, police-community relations and even a prosecutor’s personality.

“No matter what they want to do, they have to say, ‘Can this case be proven?’ And most of the time, it’s not proving the use of force,” O’Donnell said. “It’s disproving the cops’ claim that it was legitimate. … Proof beyond a reasonable doubt looks like an awfully big mountain to climb.”

Landau, meanwhile, said he is disappointed but not defeated. He said he will continue to encourage others to come forward if they feel they have been wronged by police.

“There’s got to be a way to make (the department) take these cases more seriously,” he said.

Sadie Gurman: 303-954-1661, sgurman@denverpost.com or twitter.com/sgurman