On Wednesday, federal prosecutors in Manhattan and state prosecutors in the Bronx announced a joint takedown of 14 defendants who were accused of involvement in a gang that carried out murder and assault. Eight defendants were led into federal court to be arraigned, one by one, wearing face masks.

The decision to postpone most trials, though sensible from a public health standpoint, could ultimately lead to complications should the defense decide to argue that the measure violates speedy trial rules, legal experts said.

The suspension of grand juries also raises serious legal issues, the experts said.

In New York, state prosecutors have 120 hours to either indict or release a defendant held in jail on a felony charge. But under the new rules put in place because of the coronavirus, grand juries in New York can be convened only under “exceptional circumstances,” and those have not yet been defined.

Tina Luongo, chief criminal defender of the Legal Aid Society, said the police and prosecutors should not “add a single person to Rikers at this point.”

“The real concern is what is the effect of arresting someone and setting bail and there is not going to be a grand jury impaneled,” she said.

On Wednesday, David M. Hoovler, president of the District Attorneys Association of New York, sent a letter to Gov. Andrew M. Cuomo asking him to issue an executive order that would suspend the 120-hour rule for indictments as well as delay speedy trial deadlines. The group also asked the governor to relax rules that require prosecutors to turn over evidence and information about witnesses to the defense.

“I cannot stress the urgency behind the need to act on this matter to ensure that justice is served and that we are minimizing the spread of Covid-19,” Mr. Hoovler wrote.