If you have heard of Bruce Castor, you have likely heard of Bruce Castor.

Montgomery County’s former top prosecutor is sort of famous, sort of infamous in the Philadelphia suburbs’ legal and political circles, and he’s now taking his brand of public engagement to perhaps the largest stage in the country: the second impeachment trial of former President Donald Trump.

The former president, who is hunkered down in Florida, announced Sunday Castor will serve as co-lead counsel alongside a criminal defense attorney from Alabama — an appointment made after Trump’s previous legal team parted ways with him, according to the Washington Post, after he insisted they focus their defense on lies that the 2020 election was stolen.

It’s not clear yet whether Bruce L. Castor Jr., a Republican, will follow the ex-president’s preferred playbook. But here’s what you need to know about the lawyer from the Philly ‘burbs, whether you’ve heard of him or not.

» READ MORE: Pa. Republicans are stumped by Trump’s pick of Bruce Castor for his impeachment defense. Others see a ‘natural choice.’

1. He’s best known for declining to prosecute Bill Cosby

Castor, 59, was the top law enforcement officer in Montgomery County from 2000 to 2008, but one decision will follow him for years to come. In 2005, two decades after he was first hired in the county District Attorney’s Office, police fielded a report that comedian Bill Cosby had sexually assaulted a woman in his Cheltenham home about a year prior.

During a 2016 hearing in the eventual criminal case against the disgraced comedian, Castor said he didn’t think the case was winnable and that he cut a deal with Cosby: He declined to press criminal charges on the assurance Cosby wouldn’t plead the fifth during a civil suit filed by the woman, former Temple University employee Andrea Constand.

There was no evidence of any written or oral agreement presented, which didn’t sit well with the judge, who determined Castor’s testimony to be uncredible and inconsistent.

Of course, Cosby was eventually charged and dozens of women told reporters, investigators, and the world that he drugged and sexually assaulted them. Constand’s case was the one that ultimately sent Cosby to jail. He was convicted in 2018.

Castor later sued Constand, claiming she tried to interfere in his bid for reelection. The case went nowhere.

2. He’s a perennial political candidate

In the middle of his service in Montgomery County, Castor ran for state attorney general, losing in the GOP primary to Tom Corbett, the Western Pennsylvania Republican who went on to become governor. In 2007, Castor ran for public office again, this time winning a seat on the Montgomery County Board of Commissioners, a three-member, county-level governing body.

His first term was fraught. The other two members, Democrat Joe Hoeffel and Republican Jim Matthews, established an agreement that essentially iced Castor out of policy decisions. An Inquirer headline in 2008 referred to Castor as the “squeaky third wheel.”

The makeup of the board changed in Castor’s second term, with the other two seats claimed by Democrats Leslie Richards and Josh Shapiro, the latter of whom is now the Pennsylvania attorney general and widely considered a 2022 gubernatorial candidate. This being Montgomery County, Castor was not known to be among the far-right wing of the Republican Party, and the three commissioners got along well. (Though it’s unclear how Shapiro, who roundly rebuked Trump’s claims of election fraud, will feel now about his former colleague.)

In 2014, Castor — who once said he was “seduced” by the idea of being the governor — floated challenging Corbett in the GOP primary. He decided not to.

Then, a year later, he tried to reclaim his old job as Montgomery County district attorney, running against Democrat Kevin Steele in the general election. Steele, who made Castor’s decision in the Cosby case a central campaign issue, won, and Castor’s three-decade run in public service came to an end.

3. He eventually became attorney general, sorta

In May 2016, embattled former Attorney General Kathleen Kane created a new position called solicitor general, her No. 2, and announced Castor would fill it, even though Castor later said the two had met only twice. He made the majority of the top legal decisions while Kane’s law license was suspended as she faced criminal charges in connection with allegations she orchestrated a grand jury leak to hurt her political opponents.

Three months later, Kane was convicted of perjury and abuse of office and resigned, making Castor the acting top dog and putting him in a job he made clear he’d wanted for more than a decade. He even delayed the public swearing-in ceremony so his elderly parents could attend, saying at the time: “They’ve waited 12 years for this to happen.”

Castor’s honeymoon in Harrisburg didn’t last long. Less than a week later, Gov. Tom Wolf appointed Bruce Beemer — Kane’s No. 2 before her No. 2 was Castor — to serve as acting attorney general and fill out the remaining months of Kane’s term. (Yes, this was a little messy.) Castor returned to private practice.

4. He’s worked high-profile cases, but nothing like this

Sure, he declined to charge Cosby, but Castor’s office did prosecute some of area’s most notorious cases.

His office secured convictions against a number of murderers, including serial killer John C. Eichinger, who in 2005 was sentenced to death for killing four people, including a toddler. He remains on death row.

Castor also worked in private practice for years and defended a number of high-profile clients. In 2009, he represented former Grizzlies player Marko Jaric, who was accused of sexually assaulting a woman in Philadelphia when the team was in town playing the Sixers. Jaric was not charged.

In 2015, he represented Stacy Parks Miller, the former district attorney of Centre County who was targeted by civil suits and ethics investigations after being accused of forging a judge’s signature.

Since the Cosby imbroglio tamed, Castor has worked at the Center City law firm van der Veen, O’Neill, Hartshorn and Levin. In August, the firm sued Trump and the U.S. Postal Service, arguing delivery delays could imperil mail ballots in the forthcoming election.

Castor, though, has never defended a client quite like Trump, now the only president in American history to be impeached twice. But the pair may be kindred spirits. Like Trump …

5. … Castor is unpredictable

He’s aggressive and indignant and often wearing pinstripes. Castor likes the spotlight and is not known for holding back, often creating the buzz that follows him. In 2008 when he was feuding with his fellow county commissioners, for example, he made sure the public knew that he hung the certificate making his job title official next to a toilet.

And in 2015 as criticism mounted for his handling of the Cosby allegations, he posted on Facebook that a reporter came to his home — which journalists often do to give a person facing public scrutiny a chance to respond — and that this did not make him very happy.

“This reporter will never know the danger he was in,” Castor wrote. “ … I have said everything that needs saying about this case. So reporters: stop calling my elderly parents, and never even consider coming to our house uninvited especially on a work day when my wife is alone, except for Mr. Ruger.”

Ruger is a gun manufacturer. There was outcry over the posts, and Castor shut down his Facebook and Twitter in the aftermath.

Since Trump’s announcement Sunday night, Castor has uncharacteristically said little, releasing a statement saying it’s a “privilege to represent the 45th president.”

“The strength of our Constitution is about to be tested like never before in our history,” he said. “It is strong and resilient — a document written for the ages, and it will triumph over partisanship yet again, and always.”