ROCKVILLE, Md. — After three years of searching, officials finally found an interpreter for the sexual abuse case against a Liberian man who is one of only about 100,000 people worldwide who speak Vai.

But it was too late.

A Montgomery County judge dismissed the charges against Mahamu Kanneh last month, saying problems securing Vai interpreters contributed to repeated delays that violated his right to a speedy trial.

Kanneh learned of the decision through the interpreter.

The ruling, which prompted outrage from the public, illustrates a major challenge professional interpreters say the judicial system faces — finding people qualified to translate unfamiliar languages that are showing up more frequently in courts. It's a problem that can delay cases for long periods and, in some instances, affect the outcome.

In Arizona, a judge threatened to drop human-smuggling charges against three men earlier this year because of problems locating Mayan-dialect interpreters.

Authorities in Arkansas have struggled with two cases against natives of the Marshall Islands accused of killing children.

And prosecutors in Louisville, Ky., had difficulty earlier this year before finding a Bantu interpreter for a Somali man charged with killing his four children.

Interpreter organizations say it's difficult to estimate the number of cases affected by courts' inability to secure translators of obscure languages. That's because most of the cases are mundane and attract little attention. But it is not uncommon for cases to be affected by shortages of qualified interpreters, they said.

"The person who ends up getting hurt in this usually is the defendant," said Kevin Hendzel, a spokesman for the Virginia-based American Translators Association.

Federal law requires public agencies receiving federal money to provide equal access to people with "limited English proficiency." Most courts concluded that means interpreters should be available for all court proceedings when needed, most often at the court's expense, Hendzel said.

Interpreters often are at a defendant's side for an entire case, from an arrest through trial. Ideally, they must be able to keep a running translation of what is said, and be familiar enough with legal or other court terms to be able to convert phrases like "blood splatter" into a foreign language.

Courts often turn to agencies, lists by state judiciaries or online services to find interpreters. With hard-to-find languages, they have to cast wider nets, contacting community organizations or embassies. Often interpreters must be flown in for cases.

Moving beyond the usual sources can prove unreliable. Ideally, courts hire full-time interpreters who are certified by the state or a professional organization. But in cases involving rarer languages, some courts end up hiring people with little or no court background.

"In some cases, you're not going to find anybody who is experienced in court proceedings. They have never set foot in a court," said Isabel Framer, head of the National Association of Judiciary Interpreters and Translators, a group representing 1,200 interpreters who speak 65 languages.

Many interpreters of rarer languages also have other jobs, meaning courts must work around their schedules.

"It's not just finding; it is seeing if they want to come, when they want to come and bringing them in," said Mara Simmons, who coordinates interpreters for the Arkansas court system.

Kanneh, of Gaithersburg, was accused in 2004 of assaulting a 7-year-old girl and a 1-year-old girl, both relatives of his.

On June 17, Circuit Judge Katherine Savage reluctantly threw out the case. Prosecutors have appealed the decision.