New York Times Feature Article: A Self-Proclaimed ‘Tough Cop’ Wants a New Title: Mayor

*New York Private Detective Services founder; "Mark Pucci", interviewed regarding his former role as Executive Vice President & Chief Investigator for Mr. Dietl's firm.

When Stephen K. Bannon got into a dispute with an ex-wife who accused him of domestic violence, he hired a private investigator with a history of digging up embarrassing information about people claiming to have been wronged.

When the Fox News chairman Roger E. Ailes was accused in lawsuits of sexually harassing the network personalities Gretchen Carlson and Andrea Tantaros, lawyers for the company hired the same detective to spy on the women.

And when Don Imus, the radio host who used to be on the Fox Business Network, found himself in a disagreement with a former associate, he retained the investigator to talk the man into backing down.

The investigator was Bo Dietl, 66, a retired police detective and former Fox News contributor who is now immersed in a sideshow-like bid for mayor of New York City. Mr. Dietl is running as an independent, but he has raised $800,000, and some think he can ride his high name recognition and colorful personality to an upset victory.

Mr. Dietl’s work was not atypical of a private investigator; many are paid to undertake defense investigations of plaintiffs. But in repeatedly snooping on behalf of prominent men in conservative media, Mr. Dietl has been accused of pushing the limits of what private investigators are allowed to do, according to court records and interviews with two dozen former members of his investigative firm’s staff.

Mr. Dietl, who is campaigning as a self-proclaimed “tough cop,” has followed people who say they’ve been victimized, tracked down their ex-lovers and leaked gossip about them to the media, the former staff members said. On multiple occasions, he has been accused of intimidation and harassment, the records show.

Mr. Dietl confirmed his involvement in each case described in this article, including the investigations for Mr. Bannon and Mr. Imus and into Ms. Tantaros, none of which had been disclosed previously. (The Wall Street Journal reported the investigation of Ms. Carlson last month.)

In a series of interviews, Mr. Dietl defended himself as a professional and said he had never tapped phones, hacked computers or done anything illegal. He also emphasized that he had been hired to investigate the former Fox News employees by company lawyers, not directly by Mr. Ailes.

“Everybody has a right to defend themselves under the Constitution,” he said. “We were hired not to ‘dig up dirt’ but to find the truth and facts about the person who is suing.”

Mr. Dietl also said he had saved countless women as a police officer and had helped dozens more as an investigator. It would be unfair to focus on a few cases in a 32-year career, he said.

Still, critics described Mr. Dietl’s conduct as troubling.

“It is a disgusting way to defend a lawsuit,” said Nancy Erika Smith, Ms. Carlson’s lawyer. “It is disgusting for Fox. It is disgusting for Bo Dietl. It is just another way to attack women, and I think women are pretty sick of it.”

The revelations could further complicate a campaign already hampered by a self-inflicted wound: Mr. Dietl did not correctly file party registration documents, forcing him to run as an independent. Mayor Bill de Blasio, a Democrat, is seeking re-election, and the top Republican challengers are Assemblywoman Nicole Malliotakis and the real estate sales executive Paul J. Massey Jr.

As a candidate, Mr. Dietl has made a racially charged comment involving the mayor’s wife, sent an obscenity-laced text to the chairman of the Reform Party on Staten Island and been criticized for failing to pay $477,000 in state taxes, among other issues.

Mr. Dietl’s record as an investigator has not been closely scrutinized, however. A review by The New York Times of some of his high-profile cases provides insight into Mr. Dietl and his investigations, including work done for members of the Trump administration and, according to Mr. Dietl, Donald J. Trump.

In the one case in which he worked directly for Mr. Trump, Mr. Dietl said, someone was causing “trouble” for a Trump casino in Atlantic City. Mr. Dietl, who did not describe the trouble, said he had called the man and threatened to release compromising information about him if the problem did not go away. The problem went away, he said.

Mr. Dietl has had a longer history with Mr. Bannon, who is now the president’s chief strategist.

Mr. Bannon declined to comment on Mr. Dietl. But according to friends, they met in California in the 1990s, when both were moving in entertainment industry circles.

“I was selling my movie,” Mr. Dietl said, referring to “One Tough Cop,” a film based on his autobiography that starred Stephen Baldwin. “He was a producer, director.”

Mr. Bannon soon hired the investigator to work on “domestic” issues related to a divorce, said Mr. Dietl, who declined to elaborate.

The only divorce at that time was Mr. Bannon’s 1997 split from his second wife, who had accused him of attacking her. Former members of Mr. Dietl’s staff confirmed that the firm had been hired to investigate Mr. Bannon’s wife during a legal dispute related to the case.

In the case, Mr. Bannon was charged with committing domestic violence and battery and dissuading a witness, his wife, from reporting a crime. But the case was dismissed when his wife did not attend a court hearing, records show. She later said in divorce papers that she had not gone because Mr. Bannon told her that “if I went to court, he and his attorney would make sure that I would be the one who was guilty.”

Afterward, Mr. Dietl continued to do a variety of work for Mr. Bannon for years, according to former members of Mr. Dietl’s staff. One investigator said he had talked to Mr. Bannon “hundreds of times” over the years.

Mr. Dietl has worked for several people of notoriety, including Jordan Belfort, the “Wolf of Wall Street” stockbroker, who pleaded guilty to fraud; Joshua Cantor, a business executive who also pleaded guilty to fraud; and Melvyn Weiss, a lawyer who pleaded guilty to paying kickbacks.

Mr. Dietl has been accused of inappropriate behavior, court records show. In one case, Ford Motor accused his investigators of “barging into” witnesses’ homes. In another, a co-founder of Arizona Iced Tea accused him of intimidation. Last year, Mr. Dietl paid the New York Department of State $1,000 to resolve a complaint from a former client who claimed the firm had failed to do the work she commissioned.

Mr. Dietl’s most prominent work has been for the scandal-plagued Fox News.

According to Mr. Dietl and several former staff members, the firm was first hired in 2004 by the network’s outside counsel, Epstein, Becker & Green, to investigate Andrea Mackris, a producer on “The O’Reilly Factor” who had accused the host, Bill O’Reilly, in a lawsuit of making sexual comments to her.

Mr. Dietl’s investigation began with routine checks to see if Ms. Mackris had been arrested or had filed frivolous lawsuits. But when those tactics turned up little information, Mr. Dietl asked his staff to do more.

“One Friday evening I was sent to a bar in Columbus Circle to watch her for about two hours,” said a former vice president of the firm who spoke on condition of anonymity, saying he feared retaliation. “They were hoping that I would be able to record her partying, carrying on.”

“She wasn’t doing anything wrong, as far as I could see,” he said.

The former vice president said he did not know how his boss had used the little information he collected or how many other times investigators followed Ms. Mackris. But soon, stories started appearing in the tabloids claiming that Ms. Mackris was in debt and potentially trying to shake down Mr. O’Reilly.

It is unclear if the stories affected the lawsuit, which ended with Mr. O’Reilly’s paying a $9 million settlement to Ms. Mackris. Fox News did not return repeated messages seeking comment.

Regardless, the project was lucrative for Mr. Dietl. In addition to getting a fee, he was soon named a Fox News contributor, a job that paid $700 per appearance and greatly expanded his visibility to potential clients. For years afterward, former staff members said, Mr. Dietl provided free investigative services to Mr. Imus, the Fox News host Sean Hannity and others.

Mr. Dietl declined to detail his work for Mr. Imus other than to say he often helps out friends who get into trouble by talking to the other people involved and telling them that if they mess with his friend, they mess with him.

“When people have problems, they come to Uncle Bo,” Mr. Dietl said.

Mr. Imus declined to comment.

One Fox-related case exploded in public: In 2008, reporters received an email that accused the wife of Rupert Murdoch, the chairman of Fox News’s parent company, of being a “nymphomaniac.” Gawker later reported that Mr. Dietl had been involved in circulating the email — which Mr. Dietl confirmed in the interviews with The Times.

Then, last summer, sexual harassment allegations arose, first from Ms. Carlson, who sued Mr. Ailes, and then from others, including Ms. Tantaros, who leveled accusations against Mr. Ailes and Mr. O’Reilly in her lawsuits.

Again, Fox News hired Epstein, Becker & Green, and again the lawyers summoned Mr. Dietl.

Mr. Dietl cast a wide net for the inquiries into Ms. Carlson and Ms. Tantaros, which occurred simultaneously, according to former staff members, including Mr. Dietl’s top investigator at the time, and fellow former police officer, Mark Pucci.

Mr. Pucci said he had compiled a list of leads and ultimately traveled to Virginia to try to find someone he believed to be an ex-boyfriend of Ms. Carlson’s. Other investigators combed through records and videos. One investigator tried to persuade the ghostwriter of Ms. Tantaros’s book to provide compromising information about her. Several staff members followed the women in hopes of overhearing them discuss plans for extravagant purchases.

In all, Mr. Pucci said, nearly a dozen investigators spent almost a month on the cases before filing reports to the lawyers.

“We did our job to get the truth,” Mr. Pucci said.

Ms. Smith, the lawyer for Ms. Carlson, said she had been prepared for her client to be followed and had taken precautions, including increasing security at her home and business.

She called Fox News’s tactics “pathetic.” Fox News eventually settled with Ms. Carlson for $20 million, and Mr. Ailes resigned last July. Mr. O’Reilly was forced out in April after The Times disclosed a pattern of sexual harassment allegations against him, and an internal investigation uncovered more. Ms. Tantaros’s lawsuits are still pending.

Emily Steel contributed reporting. Susan Beachy and Kitty Bennett contributed research. A version of this article appears in print on June 25, 2017, on Page A1 of the New York edition with the headline: ‘Tough Cop’ Running for Mayor Is Accused of Pushing Limits. Order Reprints| Today's Paper|Subscribe