NEW YORK — The two federal courthouses in Manhattan took the adage that justice delayed is justice denied to heart when the coronavirus hit, creating a pandemic-safe environment for jurors that could be a blueprint for courts elsewhere.

After months of inactivity, they are holding trials again with a safety system that includes an air-filtered plexiglass booth for witnesses, an audio system that lets socially distant lawyers exchange whispers without putting their heads together and protocols to ensure that no document changes hands without being sprayed with disinfectant.

More than 100 trials are scheduled this year, and a month after jury trials resumed following a post-Thanksgiving halt, there has been no traceable spread of COVID-19 at the courthouse, according to its chief administrator, District Executive Edward Friedland.

That’s important because some of the nation’s oldest judges are among the 70 or so who sit in the two courthouses. One, 93-year-old Louis Stanton, has come into work almost every day since the pandemic arrived.

When trials initially halted a year ago as the pandemic hit the city, Chief Judge Colleen McMahon formed a committee to explore how to resume safely. Friedland tapped the federal Centers for Disease Control and Prevention for expertise. Soon, an epidemiologist was on board, along with an airflow expert.

A CDC expert who had designed airtight hospital bed units with HEPA filters helped develop plexiglass booths where witnesses safely sit maskless, preserving a defendant’s right to confront an accuser.

McMahon credited the extensive anti-COVID efforts for allowing incarcerated defendants to go to trial first.

Only nine jury trials were conducted in the fall, but there have been seven since mid-February, including four underway this past week. Normally, there’d be dozens annually.

At the courthouses, some jurors are rescheduled if they don’t want to attend a trial in person.

“It was a gamble as to whether we were going to have people answer the call or not,” McMahon said, but she said there have been enough people to ensure diverse juries.

Six of 40 courtrooms in a courthouse that opened in the mid-1990s have been reconfigured, as have two others across the street in an 85-year-old courthouse listed on the U.S. National Register of Historic Places.

Jurors fill nearly half of each courtroom, spaced apart in an elevated section. Each receives a packet with hand sanitizer, masks, gloves, disinfectant wipes and a forehead thermometer. Double masks are mandatory. Some courtrooms were recast into giant spaces for jurors to congregate 6 feet apart for discussions, 12 feet for meals.

When a juror recently tested positive for the coronavirus, no other jurors got sick.

In court, lawyers at long tables whisper into special phones, their voices amplified for their team by a technology borrowed from roadies communicating backstage at long-ago rock concerts. Microphone covers are replaced with each speaker.

“We think we’ve done a lot of things here that are groundbreaking in terms of how to conduct a trial during COVID, but certainly we’ve spoken to our colleagues in other courts and learned from them as well,” Friedland said.

About $1 million was spent on the changes.

“You can’t go anywhere in this courthouse now without seeing a sign. The one thing we’re worried about is complacency — that people have COVID fatigue,” Friedland said.