Like many other departments across the country, the New York Police Department has taken steps to improve fairness.

“It is absolutely not in our best interest to do something that is going to be suppressed,” said Dermot Shea, the city’s chief of detectives.

To minimize differences between the suspect and fillers, detectives will cover up tattoos and use hats to obscure differences in hair styles, Chief Shea said. “Fairness is driving everything that we do to make sure that we get the best prosecutable case, and that includes having a fair lineup,” he said.

But suggestive lineups are not yet a thing of the past, as the shackle on the floor in the Queens lineup would seem to indicate.

Detectives, for instance, sometimes still place teenage suspects in lineups alongside grown men, The New York Times found. A year ago, a 17-year-old robbery suspect in Brooklyn was the only teenager in the lineup. Three of the five fillers next to him were in their 30s.

Lineups, say experts who study witness memory, can be thought of as an experiment administered by the police. Detectives have a suspect. Now they want to use the memory of a witness to test whether their suspect committed the crime.

“In the witness's mind is a recollection, an image,” said William Brooks, the police chief of Norwood, Mass., a town of 30,000, and a longtime advocate for improving lineups. “You can’t see it or touch it, so how do you use it? You give it a stimulus, and you see the reaction, and see if there is a match.”