Dr. William J. O'Brien III has a way with words and a way with women.

During an October 2014 appointment, he offered a patient blue Xanax pills in exchange for oral sex, describing it as "blues for a blow."

Unfortunately for O'Brien, a former Democratic candidate for Bucks County coroner, the patient was an FBI agent secretly recording the conversation at the doctor's Bustleton office.

Federal prosecutors say O'Brien, 51, also propositioned local strippers for office sex in exchange for narcotic painkillers. Some complied, authorities say.

"They usually had the money for the visit, but the defendant wanted sex," Assistant U.S. Attorney David Troyer said Monday in the opening of O'Brien's trial.

But O'Brien's sex life is the least of his problems.

The La Salle University graduate is accused of running a multimillion-dollar pill mill with the help of the Pagans Motorcycle Club, doling out scripts for oxycodone and methadone as if they were Tic Tacs.

One of his "patients" was a burly Pagan who boldly stated on his intake form that he "had been pregnant several times," Troyer said. Another patient died from what prosecutors described as a deadly cocktail prescribed by O'Brien.

"The defendant was, in reality, nothing more than a drug dealer himself," Troyer said, describing O'Brien's office as a "veritable supermarket" for dealers and addicts

O'Brien - indicted in a separate case for allegedly placing patients inside a propane container he'd passed off as a homemade hyperbaric chamber called "Hyperox 101" - fired back at prosecutors Monday with a full-throated opening argument. He is serving as his own attorney.

"Bully! Bully! Bully!" O'Brien said, jabbing a finger at the prosecution table as he launched into a 45-minute polemic that drew from P.T. Barnum, Mark Twain, the Old Testament, and the TV show M*A*S*H.

"The bullies are going to learn a lesson. I'm not going to be bullied," said O'Brien, who spoke beside an easel on which he had helpfully written the word Bully in large letters to hammer home the point.

O'Brien, who is twice divorced but said he's still in love with his second wife, admitted propositioning the FBI agent for oral sex. "It's not a crime," he told the jury.

Jailed without bail since January 2015, O'Brien said he had lost 160 pounds from a hefty 380. He said federal agents were out to "pick on the fat guy," and had referred to him as the "fat doctor" during the long-running fraud-and-drug probe.

"These are the same people in grade school and high school that picked on me," he said. "I became a doctor. They went and got guns and badges."

At times, O'Brien's opening argument resembled a populist stump speech. Like a modern-day Willie Stark, he framed his case in David-and-Goliath terms, and noted that politicians were spending large sums of tax dollars to put him in jail while jurors receive a measly stipend.

"You guys are getting peanuts," O'Brien told the jury.

The prosecution's case might appear strong at first glance. O'Brien's codefendants have pleaded guilty and are cooperating with the government. Surveillance footage from a pole camera placed outside one of O'Brien's offices in South Philly shows Pagans members coming and going.

O'Brien said he simply treated members of the outlaw motorcycle club like other patients.

"I don't know who else I shouldn't treat," he said. "Blacks? Gays? Jews?"

O'Brien also has sought permission to use "four copies of a hardback Dr. Seuss publication" during his defense, according to a court filing last week. The reason is unclear.

The trial is expected to last six weeks.

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