Police arrested Smith in San Jose early Friday morning.
The 23-year-old's pickup truck smashed into a tree on Bentley Ridge Drive in the city's Silver Cree neighborhood. A homeowner heard the noise at about 7 a.m. and found Smith seemingly asleep at the wheel.
"I see a lot of smoke and then the neighbor came out and tried to knock on the door, and he woke up, turned off the engine," homeowner Kim Dinh said.
Police said his blood alcohol level was nearly double the legal limit. They also found marijuana in his vehicle.
After bailing himself out, the 23-year-old was back at practice at the team's training facility in Santa Clara Friday afternoon.
Head coach Jim Harbaugh said NFL policy means the league will decide if Smith will be suspended.
"There will be consequences, there always is," Harbaugh said. "Good or bad, we all have consequences."
The head coach added that he was disappointed in Smith and encouraged him to face his teammates Friday afternoon and soldier through it.
Teammate Vernon Davis says he doesn't know the details of Smith's arrest yet, but thinks the younger player will settle down.
"Even for myself coming in as a young guy, I had to go through some things," Davis said. "But there comes a point in time where you have to really just say, okay, this is it. You know, I have to get myself on the right track."
Teammate Carlos Rogers says that as a young player, it was hard for him to resist the temptation to party.
"I always had older guys that, you know, I listened to and stuck with me and I stuck to what they said and followed their directions," Rogers said. "If I'm going out, why not pay $100 and get a driver?"
This is Smith's second DUI arrest. The linebacker, who played in his first Pro Bowl and helped the Niners appear in the Super Bowl last season, was also arrested on suspicion of drunken driving in Miami Beach in January 2012. As a first offender, that charge was reduced to reckless driving.
Then in June of last year, the linebacker and another man were stabbed at a party at Smith's hilltop home in east San Jose. Shots were also fired. Two party guests have sued Smith for their injuries.
Because of Smith's arrest for DUI and for possession of marijuana, and prior brushes with the law, he may be facing suspension by the NFL. That is a decision that we may not have until possibly after Sunday's game.
Smith will be back in court in November.
(The Associated Press contributed to this story)