This story has been updated.

In a stunning development that dramatically shakes up the criminal justice system, several Bay Area courts are either closing, postponing trials or sharply scaling back legal proceedings to help stem the spread of coronavirus.

Until the Friday announcements, the state’s court system signaled no intention to curtail their access to the public or disrupt court hearings, but that changed following a multitude of declarations from public health officials banning or strongly advising against large and now even medium-sized gatherings.

With the courts becoming the latest casualty of the coronavirus, it could have significant ripple effects. As cases and trials are delayed, defendants could be forced to stay in custody longer, and police officers may end up making arrests for only the most severe crimes to avoid crowding the jails with inmates who might not be able to be arraigned in the time frame required by law. Several Bay Area legal experts were astonished by the news of the court slowdowns because of COVID-19 (coronavirus) concerns.

“This is uncharted territory for the modern American court system,” said David Ball, an associate law professor at Santa Clara University. “Any historical analogy is going to be kind of strained.”

The Contra Costa County Superior Court on Friday requested from state Supreme Court Chief Justice Tani Cantil-Sakauye “an emergency order providing that, at least until April 1, 2020, the court closure will have the effect of being a public holiday as far as statutory or other timelines.”

“The court appreciates the careful balance that must be maintained between the timely administration of justice and the protection of public health and safety,” the Contra Costa court said in a statement Friday. “Importantly, this closure is not in response to a specific notice of exposure at any court facility or to any court staff. Instead, it is in an abundance of caution to help limit the spread of the virus and the potential for future exposure.”

According to the Contra Costa Superior Court, one courtroom will be available for in-custody arraignments for adult and juvenile defendants and their attorneys but will remain closed to the public. The court added that jurors ordered to appear in court March 16 for a criminal trial still have to report, at which time “judges in those cases will provide guidance as to any further proceedings.”

But attorneys involved in ongoing murder trials told this news organization that on Friday afternoon, clerks were calling jurors to inform them not to show up. There are four such trials in Contra Costa County, including two that were in the late stages of jury selection. The trials may resume at the end of the two weeks, but details are unclear.

In Santa Clara County, starting Monday and lasting until April 5, the Superior Court is rescheduling most cases save for a select number of criminal cases. Cases affected by the rescheduling include civil, probate jury and court trials — except those that already have begun — as well as small-claims motions, trials and appeals, nontrial traffic matters, most family hearings, guardianship and adoption proceedings, and “many” criminal trials, according to the court.

“Although court proceedings are an essential service of government, the court has decided to limit the number of non-mandatory proceedings for this time in an effort to minimize the risk to all court users, court staff and judicial officers,” reads a statement from the Santa Clara County Superior Court.

Late Friday afternoon, the San Mateo County Superior Court requested an emergency order from the chief justice to suspend all civil and criminal trial proceedings starting next Wednesday through April 14th, according to Court Executive Officer Neal Taniguchi. In the meantime, the court will continue to operate in a limited capacity — with reduced staff and teleworking — but all jury trials would be put on hold, including three now underway, if the order goes into effect.

On Saturday, the Alameda County Superior Court announced a series of postponements and continuances for proceedings scheduled between Monday, March 16 and April 3 to reduce the number of people coming to courthouses. The start of jury trials for civil and misdemeanor cases, and felony cases with an out-of-custody defendant, are being pushed back eight weeks.

A statement from the court said that jurors will still be summoned for “essential” trials, and that trials already underway will continue, though jurors will be distributed throughout a courtroom as opposed to sitting alongside each other in the jury box.

Most traffic hearings in Alameda County scheduled between March 23 and April 3 will be postponed for 60 days; walk-in appearances have been suspended. Appearance dates for citations are being pushed back six months. Other court services, like the self-help centers, will also be shuttered starting Monday.

Cantil-Sakauye said in a statement Friday that any court closures or similar measures will vary with the needs of each jurisdiction.

Contra Costa County deputy district attorney Aron DeFerrari, who is also president of his prosecutors’ union, said his colleagues are “monitoring the situation closely” and are working to ensure “critical public-safety tasks are accomplished.”

Robin Lipetzsky, Contra Costa County’s chief public defender, said “less drastic measures” could have been taken that would not have adversely affected jailed defendants as much, especially since most of the jail population have not yet been convicted of a crime.

“Many of those cases will not be heard during this court closure and these individuals may now languish in custody as we wait for the courts to reopen,” Lipetzsky said in a statement. “We appreciate that we must take drastic steps to protect public health, but we must also be mindful to safeguard the due process rights and health and safety needs of those who are incarcerated, many of whom already suffer from chronic serious medical conditions and would be at a high risk were they to contract COVID-19.”

Ball said the court slowdown could also have a significant effect on defendants trying to resolve their cases through plea agreements that would release them from jail.

“If you don’t have people pleading out to time served because there aren’t court sessions, then our jails are going to get really crowded,” he said. “You do have the right to be present at your trial, and there is also a right to have the trial be public, and that extends to things like sentencing. It’s not clear to me what the limits of that are, because, again, we’re in uncharted territory.”

Steven Clark, a legal analyst and former Santa Clara County prosecutor, said he “absolutely” anticipates legal challenges to both Contra Costa County’s and Santa Clara County’s moves on the grounds that it could delay criminal defendants’ right to a speedy trial.

“This idea of ‘Let’s just call it a court holiday’ is really Constitutionally questionable — it’s not a one-day hiatus,” Clark said.

The increasing reach of the public-health emergency into the criminal-justice system was evident in the South Bay on Friday with the announcement that two Santa Clara County jail inmates were in quarantine after they were visited and interviewed by an attorney with the county Public Defender’s Office who tested positive for COVID-19.

The growing alarm prompted Silicon Valley De-Bug, a key advocacy group for inmates, to issue a letter Friday to Santa Clara County Sheriff Laurie Smith and the Board of Supervisors to begin releasing jail inmates and issue a moratorium on new bookings and jail sentences.

San Jose police Chief Eddie Garcia, whose department protects the Bay Area’s largest city, was surprised to hear the court news and criticized how it was handled, noting that many law enforcement agencies were not consulted or notified even though the decisions significantly affect officers.

“I know it’s difficult to mitigate this, but we all have a mission to do,” he said. “Our officers are not going to stop arresting people. It’s unfair for the rest of the system to come to a screeching halt while the rest of us can’t.”

Staff writers Nate Gartrell, Jason Green, Fiona Kelliher and Angela Ruggiero contributed to this report.

GET COURT INFORMATION AMID CLOSURES AND POSTPONEMENTS

Santa Clara County: www.scscourt.org/online_services/case_info.shtml

Contra Costa County: www.cc-courts.org

Alameda County: www.alameda.courts.ca.gov/Pages.aspx/COVID-19

Update: March 16, 2020 This story has been updated to add information about court postponements and other reductions in services in the Alameda County Superior Court.