Zachary Chernicky, 31, is accused of causing a fatal crash on Highway 87 in San Jose last December.
Prosecutors allege he was driving 140 mph shortly before the collision that killed Ivana Balistreri and her daughter, Liliana Balistreri.
An attorney in the courtroom said he had never seen a plea hearing draw such a large crowd. Despite the matter being continued to a later date, family members, friends and supporters of Ivana and Liliana Balistreri attended the hearing to show support.
"I miss my best friend. I miss my niece. But we need everyone to come out to show our support for them, so we can keep this guy in jail, so he's not doing this to anybody else's family," Rosie Balistreri said.
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The deaths remain fresh for relatives and loved ones who attended Tuesday's hearing.
"We were kind of in a softer place, I guess you could say. And then when everything came up again, when he got arrested, it just reopened that wound again," Balistreri said.
"I mean, I lost everything. You know, they were my everything," said Zachary Martins.
Martins, who said he was driving with his wife and daughter when Chernicky's Tesla crashed into them, expressed shock at the speed investigators say preceded the collision.
"I was shocked when we learned about the numbers. You know, 140 miles an hour at 10:45 in the morning? It just makes no sense. It's just such a lack of character and remorse," Martins said.
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"Somebody who doesn't think that a car is a dangerous weapon that could kill someone, is a danger to all of us," said Deputy District Attorney Marisa McKeown.
McKeown added family support in court is important as prosecutors seek to keep Chernicky in custody without bail.
"We believe that this defendant is uniquely dangerous. We believe that his conduct on the date of this incident, his conduct after the incident and before his arrest, show that he has a reckless disregard for human life," McKeown said.
Chernicky is scheduled to return to court Nov. 17 to formally enter a plea. A possible bail hearing would follow.
Chernicky's attorney declined to comment after Tuesday's hearing.