The goal is to protect jurors and witnesses.
For the first time we are hearing from judges who say witnesses and jurors have been intimidated by people taking pictures and sending information with their phones.
There are examples cited.
The crime amounted to an execution. The man who killed Fred Hamilton stood over him and fired several shots.
But jurors found the man, Edward Leak a Chicago police officer and nephew of the owner of well-known Chicago funeral homes guilty of murder for hire.
It was a high profile crime and Denise Maly-Politano and her fellow jurors spent long hours at the courthouse at 26th and California.
They were also possible targets of a courtroom observer who used a cell phone to take pictures of the jury inside the courtroom.
"Pretty scary. If I would have known about it at the time, because it was a concern being at the location we were, the type of case we were on and the fact we were getting out of there late at night," Maly-Politano said.
Judge Diane Gordon Cannon confiscated the cell phone, adding it to her collection. Just last week she says someone was using this phone to take video of a witness.
"Word will spread of exactly what he told under oath today in court?.I don't think we're reaching too far when we say there's intimidation here," she said.
In another case Judge Evelyn Clay had to declare a mistrial after learning someone had taken pictures of jurors with a cell phone. It was a murder trial of reputed gang member Terrence Ligon.
"Some of them said they were afraid. They were afraid of gang issues and retaliation. And just, they were afraid," Clay said.
It delayed the trial by several months and was a huge expense but jurors' fears may have been valid. A second jury acquitted Ligon but his freedom was short lived."
Three weeks after he gets out, he's killed. That's what they call street justice," Ligon's defense attorney Steve Greenberg said.
Chief Judge Timothy Evans instituted the ban on cell phones in January but after an uproar at the security check-points he instituted a grace period. In the meantime cell phones still seem to be everywhere.
"We've got to stop people from ignoring the rules now. It's come to the point where this intimidation in the courthouse must stop," Evans said.
Judges say the majority of intimidation cases come from gang-related trials.
They say it's similar to the so-called code of silence that often keeps neighborhood witnesses to gang crimes from coming forward to police for fear of retaliation.
"Every victim deserves justice. Every defendant deserves justice. No one deserves to be intimidated," Cannon said.
ABC7 News did speak to a number of courthouse regulars who are against the ban. They say they believe it's unnecessary. But the judges feel strongly about it.