Criminal defendants routinely spruce up for court appearances, donning fresh suits, shirts and ties in bids to look as mature and unmenacing as possible. Those efforts rarely merit mention. But when all five men charged with a series of 2010 killings in the District showed up for their March trial sporting large-framed, non-prescription glasses, prosecutors couldn’t let it go.

Assistant U.S. Attorney Michael Brittin asked his star witness whether he had ever known his friend Orlando Carter to wear glasses before his trial.

“Have you ever seen him wearing glasses before?” Brittin asked.

“No,” testified Nathaniel Simms, 28, who had already pleaded guilty in the case. Then Brittin repeated the question for each of Carter’s co-defendants, who sat in a line among defense attorneys and U.S. Marshals. The answer was the same.

Non-prescription “hipster” or “personality” glasses are on one hand simply a fashion fad. But they’ve also become something of a sensation in the District’s courthouse scene: Attorneys say inmates trade them before hearings, while friends and family sometimes deliver them during jailhouse visits. Some lawyers even supply them themselves.

They often escape notice — as was the case with another murder defendant who wore glasses with thick, black frames during a summer murder trial. Convicted of first-degree murder in August, his glasses never came up in court.

But the eyewear sported during the trial of Carter and his friends, which began its fifth week in D.C. Superior Court on Tuesday, has attracted attention. Court observers say prosecutors seized an opportunity to suggest to jurors that the defendants were dishonest in misrepresenting their appearance.

“They’re masks. They’re designed to confuse the witness and influence the jury,” said one prosecutor who is following the trial. Another said the defendants were “putting on a schoolboy act.” The prosecutors spoke on the condition of anonymity because the case was ongoing.

Carter, 22, and the other District men on trial — Orlando’s brother Sanquan, 21; Jeffrey Best, 23; Robert Bost, 23; and Lamar Williams, 23 — face life in prison for their alleged roles in the March 2010 string of shootings that killed five.

During dozens of hearings leading up to the trial, only Williams wore glasses; all five wear them now.

Their defense attorneys insist there’s nothing to it; several have shown photographs of their clients wearing them. It’s just “part of the professional look,” said Best’s attorney, Michael O’Keefe.

The glasses can be purchased at boutiques at high prices or drugstores for about $20. Some area defense lawyers say they can help convey the idea that the person on trial couldn’t possibly have committed a violent crime. Defendants “come out looking like Clark Kent,” said Kevin McCants.

“Sometimes I want my clients to wear them to appear more studious,” said Brian K. McDaniel.

McDaniel — who, like McCants, does not represent Carter or any of his co-defendants — says he understands why the men wear them. “Often times it’s about perception, and glasses help with that perception.”

Some studies seem to support that argument. In a 2008 study published in the American Journal of Forensic Psychology, researchers who asked students to judge a fictitious case found that African American defendants wearing glasses were considered more intelligent, more honest and less threatening than those without; white defendants with glasses were not.

All five defendants in the Orlando Carter trial are African American.

New York defense lawyer Harvey Slovis makes all his clients wear glasses: He calls them part of a “nerd defense.” The glasses, Slovis said in an interview, make people appear less intimidating. “Yes, it works,” he said.

Legal experts say it’s unsurprising that prosecutors would highlight glasses to a jury.

“This goes beyond shirts and ties,” says Richard Waites, chief executive of jury consulting firm the Advocates. “Jurors expect to see defendants wearing those. Jurors don’t expect to defendants wearing glasses if they don’t have to.”

And many jurors believe hardened criminals would seldom choose to wear glasses, said Chicago-based jury consultant Trent Kelso. “If you’re wearing glasses, you don’t look like what people might expect a criminal to look like,” Kelso said.

But some defense lawyers seem to agree with Brittin — even forbidding clients to wear glasses unnecessarily in court. “It says you’re trying to hide,” said Washington area defense attorney Gladys Weatherspoon. “It makes them look more guilty because it’s not who they are.”

And “of course a person who wears glasses can be a shooter,” Weatherspoon said. “Nobody is fooled.”

Criminal defendants’ appearances can raise eyebrows. George Huguely turned up for his February murder trial in Virginia with a youthful haircut, oversized suit and considerably less muscle than he carried in his college lacrosse days, while Lee Boyd Malvo dressed in boyish sweaters while on trial for his role in the 2002 sniper shootings that terrorized the D.C. area.

And judges are mindful of jurors’ impressions. Many of the March 2010 victims’ family members have attended the trial, and Judge Ronna L. Beck agreed to prohibit them from wearing T-shirts memorializing their dead relatives after defense attorneys objected.

That angered Patricia Jefferies, grandmother of Brishell Jones, 16, who died in the March 30 shooting.

“What about those glasses?” Jefferies asked in an interview outside the courtroom. “Those glasses are influencing the jury, trying to make them think they’re Boy Scouts or something.”

Staff researcher Magda Jean-Louis contributed to this report.