Five Sri Lankan men left hometowns reeling from the remnants of a ruthless civil war and embarked on a monthslong human-smuggling journey that spanned seven countries.

They each paid $55,000 for a ride by air and sea to a fresh chance in the Americas. They were captured within hours of their arrival in South Florida and served as witnesses for the F.B.I. in the investigation of their smugglers, cooperation that the men were led to believe would work in their favor as their cases made their way through immigration courts.

Three years later, they are still waiting for their cases to be resolved.

Studies show the average detention in federal immigration cases is one month; the five asylum seekers, despite having no criminal records, have been in immigration jails since late 2010.

Experts in immigration law say the cases highlight the subjective nature of immigration enforcement, where a detained refugee’s chance at freedom can depend largely on whose docket the claim lands, a phenomenon known as “refugee roulette.” And they raise broader questions about how the government treats undocumented immigrants who cooperate in trafficking investigations.