Who was the man wearing the Muhammad Ali T-shirt in the back of the courtroom? An ICE agent.

To public defender John Lopez, the man didn’t look like a cop, sitting in the back of Courtroom 906 in Philadelphia’s Criminal Justice Center, wearing a Muhammad Ali T-shirt.

But when Lopez walked over to introduce himself, the man flashed a badge. He was an agent with U.S. Immigration and Customs Enforcement, whose increasing sorties into courtrooms to nab undocumented immigrants have triggered outcry among judges and activists across the country, including in Pennsylvania and New Jersey.

Lopez said the ICE agent showed him a photo. It was his client.

“Is this person here?” the agent asked.

“No,” Lopez answered.

The lawyer said in an interview that his client, whom he declined to identify, was due in court on that March 21 morning to face a misdemeanor charge of second-degree assault. Lopez doesn’t know his client’s immigration status but was surprised that the federal government would spend time and money to pursue what seemed to be a small fish.

Temple University law professor Jennifer Lee is not surprised.

“This is another example of the problem of how ICE arrests at courthouses are obstructing justice for immigrants,” said Lee, a leader of the Sheller Center for Social Justice at Temple. “The Supreme Court of Pennsylvania and the individual county court systems have the responsibility and ability to address this issue.”

Today, amid the United States’ divisive debate over immigration, the halls of justice have become a contentious space. ICE says it can find and safely arrest suspects there. But immigration advocates and judges say the agents’ presence impedes the administration of justice — that fear of trouble over their immigration status can lead witnesses to violent crimes to stay away, victims of domestic violence to not testify, and children and families who need court assistance to go without.

Last year, nearly 70 former judges from 23 states wrote to ICE acting director Ronald Vitiello, saying the arrests were disrupting the criminal justice system and needed to stop.

Nationally, according to a 2018 ACLU report, ICE and Customs and Border Protection officers have dramatically expanded their presence at criminal and civil courts during the last two years, including in family, landlord-tenant, and traffic courts.

Agents have arrested immigrants in or near courthouses in states from New York to California, Arizona to Minnesota. In New Jersey, Supreme Court Chief Justice Stuart Rabner asked the agency to stay out. He wanted courthouses placed on ICE’s list of “sensitive locations,” such as churches, hospitals, and schools, which agents generally avoid.

This year in Philadelphia, at least three people have been arrested by ICE on their way in or out of the Criminal Justice Center, according to the Defender Association. On Friday morning, an undocumented man who entered the Justice Center to face charges of domestic assault was quickly detained and taken away by ICE agents, according to his lawyer, Andres Jalon.

“Apparently, ICE was waiting for him,” Jalon said. “This is the first time in Philadelphia I’ve ever had a client taken. I’ve had them taken in Bucks, but, in 20 years, I’ve never had one taken in Philly.”

Asked about Lopez’s Philadelphia courtroom encounter, ICE officials said its activities were consistent with those of other federal, state, and local law enforcement agencies.

It’s safer for agents, offenders, and the public when arrests are made in courthouses, because everyone entering the building has been screened for weapons, ICE officials said. And courthouse arrests can be necessary in jurisdictions that refuse to cooperate with ICE and allow agents into their prisons and jails.

That would include the sanctuary city of Philadelphia, where officials say that unless they receive a signed judicial warrant, they have no legal power to hold anyone beyond the time they would normally be released.

ICE officials say their courthouse enforcement includes actions against specific targets who have criminal convictions, are gang members or national security threats, have been ordered to be deported or were previously deported. Generally, witnesses in cases and family members or friends who are accompanying “the target alien” are not to be arrested unless they pose a threat to public safety or interfere with ICE, the agency said.

Agents are directed to generally avoid making arrests in civil proceedings and in places such as Family Court or Small Claims Court, according to ICE.

There’s evidence, though, that ICE actions at courthouses are being stepped up.

Its operations in and around New York courts increased 17 percent from 2017 to 2018, as the agency reached into upstate counties that had previously been untouched, according to a report by the Immigrant Defense Project. That growth underlined the agency’s “increasing reliance on the state’s court system as a place to trap and detain immigrant New Yorkers,” the study said.

In January, the Sheller Center at Temple released a report that said ICE apprehensions in and around local courthouses in Pennsylvania have frightened away undocumented witnesses and victims, disrupting the course of justice.

A Berks County man was arrested when making a child-support payment at the courthouse, the report said. And an undocumented Mexican national in Bucks County was detained when he went to the Ottsville Magisterial District Court to pay a fine for driving without a license.

“This lurking about and seizing people secretly, without giving notice before or after, is just hamstringing the daily operation of the court system,” said Robin Forrest, one of three Defender Association lawyers in the immigration unit.

Lopez, the public defender, recalled that during his encounter, the ICE agent didn’t offer his name. The man walked away after learning that Lopez’s client wasn’t there and spent the rest of the morning moving between the courtroom and the hallway.

Lopez hasn’t seen him again.