Brooklyn’s courthouses are being rocked by the “Williamsburg Effect.”

The influx of well-off and educated white people to trendy neighborhoods such as Williamsburg is rapidly “gentrifying’’ the borough’s jury pool — and transforming verdicts, lawyers and judges told The Post.

It’s good news for prosecutors in criminal cases — and bad news for plaintiffs in civil lawsuits, they said.

“The jurors are becoming more like Manhattan — which is not good for defendants,’’ noted veteran defense lawyer Julie Clark.

“They are . . . much more trusting of police,” Clark said of the jurors. “I’m not sure people from the University of Vermont would believe that a police officer would [plant] a gun.’’

Former Brooklyn prosecutor and defense lawyer John Paul DeVerna said, “The ‘Williamsburg Effect’ affects every case that goes to trial.

“A contrarian-minded person — and Billyburg has them in spades — can cause discord in the jury room. And if the hipster gets along with everyone, that can even be more dangerous because they are confident and educated, which means they have the potential to hijack the jury.”

The seismic shift also is affecting grand juries, lawyers said.

“The grand jury used to have an anti-police sentiment. When I was a prosecutor 22 years ago, a jury would be 80 percent people of color,” said high-profile lawyer Arthur Aidala. “Now, the grand juries have more law-and-order types in there.

“People who can afford to live in Brooklyn now don’t have the experience of police officers throwing them against cars and searching them. A person who just moves here from Wisconsin or Wyoming, they can’t relate to [that]. It doesn’t sound credible to them.”

Meanwhile, civil juries have become more pro-defendant.

“There’s an influx of money, and when everything gets gentrified, these jurors aren’t pro-plaintiff anymore,” said plaintiff lawyer Charen Kim.

“We’re dealing with more sophisticated people, and they don’t believe [plaintiffs] should be awarded millions of dollars for nothing.”

The percentage of white people in Brooklyn grew from 41 percent to 50 percent between 2000 and 2012, according to US Census data.

Rents in the borough also spiked by 77 percent over the same period, according to a recent report by the city comptroller’s office.

Plaintiff lawyer Edmond Chakmakian said he was so sure that the civil jury weighing his client’s case would be tainted by the “Williamsburg Effect’’ that he settled just before a verdict for damages was announced.

His client, Brian Petrides, had sued the city after he fell from scaffolding while working at a Brooklyn school and suffered debilitating injuries.

Chakmakian settled for $6 million — and later found out that the conservative jury would only have awarded his client $2 million.

“I absolutely felt like I had a much different jury on my hands than I would have had five years ago — they were MBAs and attorneys, everyone had an advanced degree,” Chakmakian said.

“There were very few minorities on the jury. It was a real white-bread jury. It’s a whole different ballgame.”

Even judges have noticed the jury shift.

“The juror pool is getting more cosmopolitan here in Brooklyn. There’s more of a blend across all socioeconomic strata,” said Brooklyn Supreme Court judge Vincent Del Giudice.

“I see a lot more highly educated people. I see more college and post-graduate degrees.”