The Boston deputy fire chief accused of posing as a state trooper and raping a prostitute at gunpoint was arrested in 1996 for soliciting sex for a fee in the city. Peter P. Pearson, 51, of 142 Village Road, East Bridgewater, admitted to sufficient facts to offering to pay for sex on Sept. 13, 1996 after he was arrested by Brockton police, according to Brockton district court records. The case was continued without a finding. Pearson, who has been a Boston firefighter for 23 years, is now accused of posing as a state trooper, ordering a Brockton prostitute into his car then driving to D.W. Field Park and forcing her to perform oral sex on him. Pearson appeared in Brockton District Court this morning, two days after his arrest Monday, where he was arraigned on charges of aggravated rape, assault with a dangerous weapon, impersonating a police officer and kidnapping while armed with a gun. Pearson, dressed in a suit jacket, ducked behind a petition in the court dock during the arraignment. He entered innocent pleas. District Court Judge Mary White ordered Pearson to be held in lieu of $50,000 cash or $500,000 surety bail. Pearson was also ordered to stay away from the victim in the case and to wear a monitoring device if he is released on bail, conditions recommended by Assistant District Attorney Shelby Smith. Shelby had asked the judge to set bail at $250,000 cash. Pearson’s defense attorney, Kate Barnes, told the court her client is ...