“Dubai’s business model relies on it being able to project an image of progressiveness and stability, and hosting expos and film festivals all fits into this,” said Nicholas McGeehan, Persian Gulf researcher for Human Rights Watch. “But cases likes this seriously undermine that image and reveal it to be nothing more than a public relations artifice.”

Emirati officials did not respond to requests for comment.

The case has only become public recently, after the family members of Mr. Cassim, the American citizen, decided that their efforts to navigate the Emirati justice system had done them little good.

“There seems to be no end in sight,” said Mr. Cassim’s brother, Shervon, who spent nearly three months in the Emirates trying to secure his brother’s release.

In a telephone interview from his home in North Carolina, Mr. Cassim said his brother’s detention had become a bitter end to his family’s decades-old relationship with the Emirates.

His parents emigrated from Sri Lanka to Dubai in 1976 because it was a land of opportunity “where you could go and make your fortune,” he said.

His mother worked for an airline and his father became an advertising executive, part of the large group of expatriates that helped expand the city from a desert backwater into the hypermodern crop of skyscrapers, malls and upscale hotels that it is today.

Shezanne Cassim’s two siblings were born there and all three were educated in British private schools, where they had close friends from the Emirates and many other countries, his brother said.