ARLINGTON, Va. (AP) -- The Ethiopian jail guard suspected of torturing and maiming political prisoners during that country's "Red Terror" era came to the United States in 2004 under a false identity, seeking asylum and claiming he would be persecuted if he returned home.
He lived comfortably in Denver until one day in 2011 when another Ethiopian who recognized him outside a cafe confronted him with the words, "I think I know you."
And that's how Kefelegn Alemu Worku, convicted last year of identity theft and immigration fraud, came to the attention of federal law enforcement authorities.
The government would like to see that happen more often.
A Justice Department lawyer recounted Worku's case at a recent presentation for refugee advocates, part of an outreach to encourage the reporting of human-rights abusers hiding in plain sight. The hope is to raise the profile of a relatively new prosecution unit and to make refugees comfortable with helping investigators -- a major challenge in human-rights criminal cases.
Part of preventing atrocities "is accountability for what people have done," Teresa McHenry, chief of the department's Human Rights and Special Prosecutions section, said in an interview.
The cases are challenging, costly and not always successful. They require prosecutors to reconstruct crime scenes from other countries that are sometimes decades old and to rely on witnesses who may be scattered across the globe. Advocates say they wish prosecutors would bring more cases. And defense lawyers criticize the Justice Department for selectively prosecuting their clients when others may be equally culpable, and for using witness testimony they argue is not always credible.
"There's a whole layer of doubt in the reliability of witnesses who now, 20 years later, talk about this stuff," said Mark Howard, who defended a woman convicted of fraudulently obtaining U.S. citizenship by lying about her role in the 1994 Rwandan genocide.
He said he was troubled when prosecutors in New Hampshire brought in new witnesses and appeared to change their legal theory at the retrial at which his client, Beatrice Munyenyezi, was found guilty. "Twenty years of cultural change and cultural education about the genocide has influenced what they say," Howard said.
The Human Rights and Special Prosecutions Section was formed in 2010 from two units, including one that specialized in hunting down Nazi criminals. But as that population has dwindled and concerns have grown about refugees who lie on visa or asylum applications to enter the United States, focus has renewed on contemporary human rights abuses.
In 2011, President Barack Obama called preventing mass atrocities a "core national security interest" and expanded the grounds on which immigrants could be denied U.S. entry, including involvement in slavery and forced labor. U.S. Immigration and Customs Enforcement created a war crimes center five years ago. And new or amended laws have expanded the Justice Department's reach.
Congress in recent years has expanded the genocide statute to permit prosecution of defendants who are in the U.S., and passed a law against the recruitment of child soldiers. Prosecutors say they hope to take more advantage of those tools but generally bring immigration-related charges -- a lower hurdle for conviction -- in cases where the crime occurred before the statutes were changed.
The human rights section has secured convictions against, among others, a former Guatemalan special forces officer who hid his role in a 1982 massacre, an ex-Salvadoran colonel who lied on immigration forms about his actions during that country's civil war; and a Bosnian man who admitted concealing his affiliation in a military brigade that committed atrocities against Muslims.
In 2008, before the section was created, prosecutors used a 1994 anti-torture law to convict the son of former Liberian President Charles Taylor for leading a notorious paramilitary unit during his father's rule.
There's also been at least one high-profile stumble.
A jury in 2011 found Lazare Kobagaya guilty of lying to immigration officials about his whereabouts during the Rwandan genocide but concluded prosecutors didn't prove he had participated in the mass killings. After the jury partially hung, prosecutors abandoned any plans to retry the case after identifying a problem with the jury instructions and acknowledging that they inadvertently failed to disclose information from a consular officer that could have been key to the defense.
A judge then tossed all of the charges, including the visa fraud conviction, at the request of prosecutors.
Despite that case, McHenry defended the section's record as "quite good" and said it expects to bring more prosecutions as legal tools expand and as refugees learn more about available resources.