07/10/2007 at 02:00 PM EDT
's lawyer forced yet another delay in court Tuesday of her pending DUI trial.
"The trial will not happen (Wednesday)" as scheduled, said Jane Robison, spokeswoman for the Los Angeles County District Attorney's Office. "Richie's attorney filed a motion ... stating that their key witness, a drug expert, was unavailable for trial."
Although Los Angeles County Commissioner Steven Lubell denied Richie's attorney's request for a new trial start date of Aug. 5, he ordered both sides to court Wednesday to argue over why the trial should be postponed again. Regardless of the outcome, the hearing postpones the trial at least a day, Robison says.
Richie does not have to attend the trial. She has reportedly traveled to Canada to watch boyfriend Joel Madden's band Good Charlotte peform Tuesday night in Calgary.
Richie's lawyer declined to respond to requests for comment. But in a court filing, she said she intends to use defense expert Terence McGee, a medical doctor specializing in drug abuse, to challenge the prosecution's scientific evidence against Richie. McGee, however, is traveling abroad and unavailable for trial, according to the filing.
"His testimony will be critical to Miss Richie's case and there is no other expert retained by the defense who can testify in this regard," Richie attorney Shawn Chapman Holley wrote.
If convicted of the misdemeanor charge, the Simple Life
star – who has pleaded not guilty – faces a minimum sentence of four days in jail with three years of probation because it would be her second DUI offense.
Last month Richie, 25, told David Letterman on his show that she is "scared" to go to jail. But, she added, "I'm willing to face whatever consequences come my way, and I take responsibility for what I've done."
Spotted driving the wrong way on a Los Angeles freeway on Dec. 11, Richie failed a field sobriety test and admitted to police that she'd smoked marijuana and taken Vicodin earlier that evening.
She was previously convicted of a DUI in June 2003.
Although California law states that repeat DUI offenders get a minimum three months in jail, that sentence can be reduced to only four days if the person accepts a three-year probation term.