Suffolk District Attorney Daniel F. Conley began his campaign for mayor with three times more money than any other candidate, an advantage that helped catapult him to the front of a crowded field.
His fund-raising secret was simple: In a decade as district attorney, Conley had not faced a challenger, allowing him to slowly amass $868,000 by the end of 2012. He can now use that money to fuel his bid for mayor.
To build that formidable campaign account, Conley mined a particularly rich vein of political donors. Since 2005, he has collected roughly $330,000 from lawyers, including contributions from some criminal defense lawyers who spar with the district attorney’s office in court, according to a Globe analysis of records from the state Office of Campaign and Political Finance.
Six of the lawyers who contributed to Conley said in interviews that they supported him as district attorney because he runs a fair and efficient office, and that they never received preferential treatment because of their donations. There is nothing illegal — or unethical — about accepting political contributions from defense lawyers or other attorneys, according to good government advocates, state law, and legal experts.
“District attorneys often will tap into the local criminal lawyer community, both prosecutors and defense lawyers,” said Daniel S. Medwed, a professor at the Northeastern University School of Law. “It would only rise to a conflict of interest if it seemed like the defense lawyers expected a quid pro quo for the donation.”
But for candidates, sometimes, the letter of the law is not enough. Medwed said a cluster of political contributions can give the wrong impression, whether the money comes from developers pushing new buildings or unions representing city employees.
“There’s still the issue of the appearance of impropriety,” the law professor said.
The Globe review found no evidence — or even a suggestion — that Conley’s office provided anything in exchange for political donations. Since Conley became district attorney, his office has handled roughly a half-million cases, making it nearly impossible to conduct an exhaustive review.
“Nobody gets any special treatment, whether you contribute or not,” Conley said in an interview. “It’s such a tiny fraction of my contribution list anyway that has business with our office. We look at every case on the merits, period.”
Conley has spent 30 years practicing law and noted that lawyers, including many longtime friends and professional colleagues, can provide the most accurate assessment of his work. “If lawyers weren’t contributing to me, frankly I’d be surprised, I’d be worried,” Conley said. “I’d say to myself, ‘Am I not discharging my duties in a way my profession supports?’ ”
Scott Harshbarger, the former state attorney general and Middlesex County district attorney, said there was nothing improper with accepting donations from defense lawyers. There are 155 prosecutors in the Suffolk district attorney’s office, and Harshbarger noted that decisions on how to proceed with most cases are made in the trenches, not directly by the district attorney.
“You don’t make most of these decisions, but you’re responsible for them,” said Harshbarger, who also served as president of Common Cause, a nonpartisan organization that promotes open and accountable government. “You don’t want them doing the politics for you, trying to figure out who supports my boss and who doesn’t support my boss. You want them out there making their decisions on the facts and the law.”
Noted criminal defense attorney J.W. Carney has contributed $2,500 to Conley since 2009. In an e-mail, Carney said he has at times disagreed with Conley, citing as one example a complaint the district attorney’s filed against Judge Raymond G. Dougan, alleging that the jurist routinely ruled against prosecutors and police in criminal cases.
“I have supported Dan Conley because he has been an outstanding district attorney for Boston,” Carney said, adding, “I never called the district attorney or met with him about a specific case in my memory.”
Former Middlesex district attorney Gerard T. Leone Jr. said he raised substantial money from the criminal defense bar and other lawyers but used a committee of legal advisers to vet contributions for potential conflicts of interest. Leone viewed the donations as a vote of confidence in his office from the people who knew it best.
“I think it’s a very good sign on a number of different fronts,” Leone said. “The reasons for the defense bar giving are they want someone they trust and have confidence in.”
Conley described himself as a methodical fund-raiser who built his bank account over a decade by holding a handful of annual events and keeping campaign expenses low. Conley said he does not have a formal process to vet donations but said he and his longtime campaign treasurer examine contributions for any potential conflicts.
“I literally read over every check. There have been occasions, rare, however, but I have sent checks back,” Conley said, adding that the donations were not from lawyers but from people of questionable reputation. “The best way to prevent any problems is to simply do what I believe we have done, which is to run an extremely professional, thorough, and ethical office.”
Since 2005, Conley has received donations from roughly 380 people who identified themselves as lawyers. The group — which included criminal defense lawyers, civil litigators, and prosecutors — accounted for roughly 43 percent of Conley’s contributions from donors who noted their occupations in fund-raising records, a legal requirement for anyone giving $200 or more.
Two other lawyers running for mayor, Councilors John R. Connolly and Michael P. Ross, have also raised significant sums from lawyers, but the donations account for a much smaller share of their fund-raising. Connolly’s donations from people identifying themselves as lawyers represented roughly 18 percent of his contributions; for Ross, lawyers accounted for 9 percent of donations.
Conley’s largest share of donations came from lawyers who described themselves as sole practitioners. Many donors, including attorney Gerry D’Ambrosio, practice predominantly civil law and spend no time in Suffolk County criminal courts. D’Ambrosio worked with Conley as an assistant district attorney in the mid-1980s and has been one of his top individuals donors since 2005, contributing $4,500.
Henry A. Sullivan, an attorney specializing in business litigation at the firm Mintz Levin, said he has contributed $4,500 to Conley because he and other lawyers care deeply about law and the operations of government.
“District attorneys wield an enormous amount of power from the state,” Sullivan said. “It’s important to have people that are smart, efficient, and reasonable — all the things you would want with someone with that awesome power.”
Lawyers from Mintz Levin have donated almost $30,000 to Conley, which is more than lawyers from any other firm. Mintz Levin’s political action committee has also contributed $1,350 to Conley’s campaign committee.
David G. Eisenstadt, a veteran defense lawyer, has donated more than $53,000 to political candidates since 2005. Eisenstadt’s contributions to Conley totaled $4,500.
“I’ve given money to John Connolly, too,” Eisenstadt said in an interview. “But not this year.”Matt Carroll of the Globe staff contributed to this report. Andrew Ryan can be reached at firstname.lastname@example.org Follow him on Twitter @globeandrewryan.