Whitney Houston's ex-husband, singer Bobby Brown, pleaded not guilty Monday to driving under the influence of alcohol weeks after her death. Brown, whose troubled marriage to the Grammy-winning star coincided with her career going off the rails with drug abuse, was stopped last month after being seen talking on a cellphone while driving near Los Angeles. The plea was entered on his behalf by Brown's lawyer, Tiffany E. Feder, on three charges: driving under the influence, driving with a blood-alcohol content greater than .08 percent and driving on a suspended license. Brown was arrested by traffic police on March 26. He was taken to jail in nearby Van Nuys, in the San Fernando Valley north of Los Angeles, but released on $5,000 bail. Brown was married for 15 years to Houston, who died on February 11 at the age of 48. A coroner's report said she drowned in her hotel room bathtub, with cocaine use and heart disease as contributing factors. Houston sold more than 170 million records worldwide but her music career spiraled out of control as she admitted drug use during an abusive relationship with Brown. The couple divorced in 2007, with Houston getting custody of their daughter, Bobbi Kristina.