David W. Johnson, one of New York Gov. David A. Paterson's closest and longest-serving aides, surrendered to prosecutors in the Bronx on Thursday and was charged with misdemeanor assault and five other offenses, the latest chapter in a domestic violence case that entangled the Paterson administration and led the governor to abandon his candidacy. Johnson's arrest was one of two new developments in the case Thursday. Several law enforcement officials said the FBI was now investigating the unauthorized access of the medical records of the woman who has accused Johnson of assault, Sherr-una Booker, by someone at Lincoln Medical and Mental Health Center. Booker went there hours after her confrontation on Oct. 31 with Johnson. The records were retrieved electronically Feb. 5, a day after The New York Times asked Paterson questions about the domestic episode. It remains unclear who obtained the records; doing so without authorization is a federal crime. After arriving at the office of the Bronx district attorney in the morning, Johnson was taken in handcuffs several hours later to a courtroom, where he was charged with assault, with two counts of criminal mischief and with menacing. All five counts are misdemeanors. He was also cited for second-degree harassment, which is a violation, a lower-level offense. A conviction on the assault charge carries a sentence of up to one year in prison. In the complaint, Booker accused Johnson, her former boyfriend, of grabbing her 'on her neck with both hands,' and she said he 'squeezed her neck, lifting her body off the floor,' according to the document. Booker told authorities she had difficulty breathing and speaking during the fight at her apartment in the Bronx. She was then pushed against her dresser while Johnson ripped off her clothing, and she bruised her leg in the melee, according to the complaint. She also said that Johnson pushed her and 'grabbed numerous phones out of her hand' as she tried to call the police. 'You're not going anywhere. I'll expletive kill you before I let you go anywhere,' she said Johnson told her. Kenneth P. Thompson, Booker's lawyer, said: 'Ms. Booker feels that she's now a step closer to getting justice for what David Johnson did to her. She also believes that no woman should ever go through what happened to her.' At his arraignment, Johnson, who at times appeared solemn, pleaded not guilty. After being released on his personal recognizance and ordered back to court Oct. 14, he refused to answer questions as he pushed through a crowd of reporters and photographers. Johnson has been suspended without pay since The Times published an article about the assault in February. At an appearance on Long Island on Thursday, the governor gave no indication that he was planning to fire Johnson, saying, 'He remains suspended pending the outcome of that case.' 