Had Superior Court Judge Patricia Schnegg upheld the motion Monday, prosecutors wouldn't have been able to introduce key evidence — including urine samples and some of Love's statements — into evidence at the trial, set for April 16.
"It would have killed our case," said Assistant City Attorney Jerry Baik. "This was a vital ruling."
The 39-year-old rock star, who didn't attend the hearing, was arrested Oct. 2 outside an ex-boyfriend's house. Police said she was wandering down the driveway unsteadily and slurring her speech.
The singer told officers she lived at the house and was trying to retrieve a compact disc, and acknowledged that she'd broken some windows, but her ex-boyfriend declined to press vandalism charges, Officer Alonzo Howell testified at the hearing.
Howell, one of the first officers at the scene, said that when he arrived Love was waving at a police helicopter hovering overhead with its spotlight fixed on her.
"She was looking up in the sky and she was waving ... with her hands straight up, like waving 'Hello,"' he said. "She had an unsteady gait and she appeared to talk with slow, slurred speech."
Howell testified that he thought Love might be under the influence and called for an officer specially trained in recognizing drug use.
But Love's attorney, Michael Rosenstein, argued that police officers had no reason to investigate his client for drug use after they decided not to arrest her for vandalism. He argued that although Love acknowledged to officers that she'd taken "hillbilly heroin," the street name for OxyContin, they didn't know she was taking it without a prescription. He also said she had a taxi waiting and wasn't going to drive under the influence.
"A thorough (burglary) investigation did take place. There was nothing going on there," Rosenstein said. "They recognized my client as high profile. She should have been released to the waiting taxi cab and sent home."
Love is charged separately in Beverly Hills Superior Court on two felony counts of drug possession for allegedly illegally possessing the painkillers hydrocodone and oxycodone. Authorities say they found the painkillers when Love was taken to a hospital after her arrest.
She also faces misdemeanor reckless endangerment and third-degree assault charges for allegedly throwing a microphone stand and striking a Kentucky man in the head during a show last month at a New York City nightclub.
Love, former lead singer of the group Hole, recently released a new album, "America's Sweetheart."