"I don't believe he intentionally tried to hit anybody," said public defender Philip Dube, who is representing Nathan Louis Campbell, 38.
"He's profoundly sad, he is profoundly depressed, that he has potentially ended somebody's life," Dube said outside the courthouse, after Campbell entered a not guilty plea. "I think this was a horrible accident."
A felony complaint outlined 34 counts against Campbell, saying he acted willfully. However, it provided no explanation for why he allegedly maneuvered around a vehicle barrier early Saturday evening and plowed into tourists and vendors on the popular walkway along the Pacific.
Italian newlywed Alice Gruppioni, 32, who was on her honeymoon, was killed, and 16 other people were injured.
Campbell was charged with one count of murder, 16 counts of assault with a deadly weapon, and 17 counts of hit-and-run.
If convicted, he could face life in prison. Bail was set at $1.48 million.
Campbell appeared briefly in court, handcuffed in blue prison garb, with his graying hair disheveled. He sat with his hands folded in his lap and only said "I do" and "yes sir" while responding to questions.
Dube told reporters there was no indication that drugs or alcohol were involved, and he said he was unaware of any history of mental illness with his client.
"He is very fragile. He is very frail right now," Dube said.
Police said Campbell has been in California only a short time, and it's not clear what brought him to Venice Beach on the summer weekend. Only a sketchy picture of him has emerged. He had no fixed address and no state driver's license, and police have found no evidence he was working in the state.
Campbell has ties to Colorado, where he lived as recently as last year. He was evicted from his apartment in Denver for not paying $655 in rent in March 2012, records show.
He was sentenced to five days in jail after pleading guilty to shoplifting at a Denver supermarket in February 2009. Five months later, he was accused of trespassing at an outdoor mall in Denver and sentenced to 10 days in jail, but instead served time in a sheriff's work program, said Melissa Drazen-Smith, assistant director of prosecutions at the Denver city attorney's office.
All of his infractions occurred in businesses along a downtown walking mall, an area that is also a magnet for homeless people.
She said Campbell is listed in one record as being a temporary laborer.
Investigators believe Campbell, who was arrested after walking into a police station several hours after Saturday's rampage, was driving his own car, Los Angeles police Cmdr. Andrew Smith said.
"I think we can safely say, when he turned himself in ... he implicated himself in the Venice incident," Smith has said.
Earlier Tuesday, the Los Angeles City Council called for new street barriers to block unwanted vehicles from getting onto the boardwalk. A motion, approved unanimously, urged police and city officials to immediately erect temporary barriers at the most dangerous intersections along the boardwalk, which draws tens of thousands of visitors on weekends.
The council also asked for a two-week study that will assess where to install permanent posts or other barriers to keep cars away from pedestrians.
When Gruppioni was hit, her husband, Christian Casadei, was at her side. He suffered minor injuries.
In a statement Monday, Casadei called his wife "an immense gift: a gift that no one can ever understand. She gave happiness and joy to anyone who had the luck to know her."
One person was critically injured and two others were taken to hospitals in serious condition. The 13 others all received less severe injuries.
Police said Campbell initially parked outside a hotel and surveyed the boardwalk, where hundreds of people were sitting at cafes, walking along the seashore or shopping for jewelry, art or other items at vending stands.
Surveillance video showed a driver getting into the Dodge, steering around a vehicle barrier and careening through the crowd.
Witnesses said the car was traveling at least 35 mph. It later turned up on a side street less than 2 miles away.
A makeshift boardwalk memorial for Gruppioni included a note in Italian expressing condolences and a painting that reads, "Venice loves you, Alice."
Associated Press writers P. Solomon Banda in Denver, Colleen Barry in Milan, and Raquel Maria Dillon in Los Angeles contributed to this report.