He was conscious and alert while being taken to University Hospital, but further updates on his condition were not available.
The jury had not yet been seated. They were told simply that an issue came up and asked to return on Wednesday.
Mitchell, 57, is on trial for the 2002 kidnapping of Elizabeth Smart. Defense attorneys have been trying to convince jurors that their client is legally insane.
Mitchell entered the courtroom singing "O Holy Night." Moments later, after U.S. Judge Dale Kimball was talking to prosecutors and defense lawyers about reading a statement to jurors that apparently would inform them about Mitchell's 2005 mental competency proceedings in state court, Mitchell went into seizure.
As Kimball was explaining his decision, Mitchell stopped singing and dropped his head for a few moments. Defense attorney Wendy Lewis locked eyes with him and then he flailed back, making a loud bleating sound. He then fell to the left and his head came back.
At 8:40 a.m., Lewis told the judge, "He's having a seizure your honor."
Then Lewis and a U.S. Marshal laid the defendant onto the floor.
"You might want to take him out and see if he needs medical [assistance]," Kimball said.
A marshal called 911. There was no sound for a minute or two, and then Mitchell could be heard breathing heavily.
Meanwhile, psychiatrists Noel Gardner and Paul Whitehead, who were in the courtroom, briefly attended to Mitchell. At 8:44 a.m., the judge called a recess.
Mitchell was still for about a minute, at which time Lewis asked, "Is he breathing?" A marshal replied that he was. Two minutes later, paramedics arrived and one said, "Immanuel, my name is Brandon. I'm a paramedic, can you answer me?"
Presumably, someone on the defense team had informed paramedics that Mitchell likes to go by the Biblical name Immanuel David Isaiah.
At that point, Mitchell was lying partially on his left side with his shoulders on the ground, his eyes closed. His right fist was clenched. The paramedic then asked Mitchell, again addressing him as Immanuel, if he could open his eyes. "Can you talk to me at all?" the paramedic asked.
At about 8:50, Mitchell opened his eyes, raised his head and the paramedics told him they were going to give him oxygen and again asked, "Can you talk to me? Tell me where you're at."
The paramedic placed the oxygen mask on his face and told him to breathe. Mitchell appeared to struggle and the paramedic said "Just leave it there, Immanuel."
Mitchell then lay quietly as another paramedic took his pulse. Moments later, he was lifted onto a gurney and told to sit back. At 8:54 a.m. he was wheeled out, his eyes closed.
About a minute later, attorney Lewis began sobbing and was hugged by another woman in the courtroom.
Lewis later explained that seeing Mitchell being hauled out on a gurney sparked a flashback of her husband, James Humlicek, who died of a heart attack four years ago. Lewis told The Tribune that, as with Mitchell, she was sitting beside her husband when he "fell into me and I helped him onto the floor."
"I was quite surprised at how I reacted," Lewis said of breaking down in the courtroom. But she added that her treating physician at the time, Gardner who happens to be a prosecution witness at Mitchell's trial assured her "it was a completely normal reaction."
Mitchell's stepdaughter Rebecca Woodridge told reporters, "They'll take him to the hospital and he'll refuse treatment. He won't take anything."
Woodridge said later she knew Mitchell had a seizure in December and again "every few months."
"This isn't something he's making up," she said about the possibility Mitchell may have faked the seizure. "These are real."
Elizabeth Smart mentioned at least one seizure in her testimony earlier in the trial. Defense attorney Robert Steele asked her if she ever saw Mitchell lose consciousness.
"We were in California at the time. He was in the middle of raping me and he experienced a seizure," she said.
She said it was the only time she had seen Mitchell have a seizure.
Outside of the courtroom, Mitchell's defense attorney Robert Steele said that while some may speculate this seizure was an act, "we watched a seizure. That is what we watched," Steele said. This was the first time Steele said he had experienced his client having a seizure.
"There was a medical physician [psychiatrists from both the defense and prosecution's witness list] in the room, that immediately went to him. I don't think anybody suspects that it wasn't [a seizure]."
Steele said hopefully what happened Tuesday morning will not affect the trial going forward. He expects the trial to resume and added that he believes Mitchell will be in court tomorrow.
Shortly after 9 a.m., Kimball said Mitchell's trial would be suspended for the remainder of the day pending the outcome of a medical examination.