As jury selection began Monday, 21 potential jurors were brought into the courtroom. Four of them -- three women and one man -- were interviewed individually by attorneys, but there were no indications how either side felt about any of the potential jurors.
From that group of 21, one person was dismissed. The same group of 20 will be back on Tuesday for more individual questioning.
"If we can pick a jury in Seminole County, this is where the incident occurred and this is where the case should be decided," O'Mara told HLN's Jean Casarez.
He also said the George Zimmerman defense fund has raised $85,000 in the past week and a half.
Media coverage of the case is expected to be intense.
The case garnered so much attention that about a month after the shooting, President Barack Obama spoke about it, saying the shooting required "soul-searching."
Zimmerman's brother, Robert, has called on the state to drop the charges.
"George lived in a community plagued by crime and was the first to come forward to help his neighbors," Robert Zimmerman said last month.
"George is a good, decent and honest man. It is now my honor to advocate for him. George is in the fight of his life quite literally."
Authorities initially "did their job when they refused to charge someone with a crime who committed no crime," he said.
"In this country, you don't charge someone why any crime solely to assuage the concerns of the misinformed masses."
CNN's Vivian Kuo and HLNtv.com's Colette Bennett contributed to this report.
Dana Ford | CNN