David Pecker, who once called Donald Trump "a personal friend of mine," flashed a big smile as he took the stand as the trial's first witness, belying the gravity of the moment.

Pecker cackled loudly into the microphone, jolting the room, when prosecutor Josh Steinglass, asked him about his various phone numbers that he struggled to remember.

Pecker, 72, was the publisher of the National Enquirer but prosecutors said he was "acting as a co-conspirator" in helping buy and bury damaging stories about Trump, including a doorman's false claim that Trump had fathered a love child and a Playboy model's claim of a sexual relationship with Trump, who has denied both allegations.

Trump, who once said Pecker would make a "brilliant" choice as editor of Time magazine, listened while leaning forward in his chair, arms crossed on the table, an unhappy look on his face.

Pecker testified that he had final say whether to publish any story involving a famous person.

"I had the final say of the celebrity side of the magazine," Pecker said. "We used checkbook journalism. We paid for stories."

Pecker is testifying pursuant to a subpoena. He has also secured a non-prosecution agreement with the Manhattan district attorney's office.

Prosecutors have called former American Media Inc. executive David Pecker as their first witness.

The DA alleges that Pecker, who oversaw the National Enquirer, engaged in a conspiracy with Trump and Trump's then-attorney Michael Cohen to help influence the 2016 election by killing negative stories about Trump.

In his opening statement, defense attorney Todd Blanche sought to eviscerate Michael Cohen's credibility, saying Cohen is obsessed with Donald Trump, has a desire to see Trump incarcerated and has a propensity to lie.

"He has a goal, an obsession, with getting Trump. I submit to you he cannot be trusted," Blanche said.

On Sunday night, Cohen publicly posted online that he had a "mental excitement about this trial" and the testimony he would deliver, Blanche said.

"His entire financial livelihood depends on President Trump's destruction," Blanche said. "You cannot make a serious decision about President Trump by relying on the words of Michael Cohen."

"I have a spoiler alert," defense attorney Todd Blanche told jurors during his opening statement. "There is nothing wrong with trying to influence an election. It's called democracy."

Amid frequent objections from prosecutors, Blanche argued that the Manhattan district attorney has attempted to make the payments and non-disclosure agreements between Trump and Stormy Daniels "sinister" to the jury.

Judge Merchan had to interrupt Blanche's opening after multiple objections from prosecutors, then he met the parties at a sidebar conference, after which he struck a line from Blanche's opening.

"There is nothing illegal about entering into a non-disclosure agreement. Period," Blanche restated after the portion of his opening was struck from the record.

Blanche's opening has come off more casual and off-the-cuff than the state's opening, with Blanche improvising and posing hypotheticals to argue that accountants at the Trump Organization did not run the invoices by Trump as he was "running the country."

"'Hey, we got this invoice. I know we are trying to cover it up here,'" Blanche said sarcastically about how prosecutors described how accountants received invoices from Cohen. "Absolutely not."

According to Blanche, Trump was unaware of how the invoices were processed by his employees.

"President Trump has nothing to do -- nothing to do -- with the invoice, with the check being generated, or with the entry on the ledger," Blanche said, arguing that Trump was busy "in the White House while he was running the country."

"The reality is that President Trump is not on the hook -- criminally responsible -- for something Michael Cohen might have done years after the fact. The evidence will prove otherwise," Blanche said.

Former President Trump's attorney Emil Bove began his cross-examination of former National Enquirer publisher David Pecker by seeking to painting Pecker and Trump's "mutually beneficially" relationship as one that had nothing to do with the election but rather had been underway for years under a "standard operating procedure."

"Seventeen years of providing President Trump with a heads-up about potentially negative publicity?" Bove asked Pecker.

"That's correct," Pecker said.

Bove asked Pecker about the first time he ever provided Trump with information -- which Pecker testified was in the 1990s and related to a negative story about Marla Maples, Trump's ex-wife.

"Fair to say that predated the Trump Tower meeting by a long time?" Bove asked of Pecker and Trump's relationship.

"Yes," Pecker said.

"A lot of interactions?" Bove asked.

"Yes," Pecker responded.

Pecker also testified about buying and suppressing stories for other individuals, such as one for former Rep. Rahm Emanuel for $20,000.

Bove also sought to show that kind of relationship between publishers and politicians was normal, saying there was "nothing wrong about" it.

"You are aware many politicians work with the media to try to promote their image?" Bove asked.

"Yes," Pecker responded.

"That's standard operating procedure?" Bove again asked.

"Yes," Pecker said.

"And sometimes when politicians are doing that, that is to try to win elections?" Bove continued.

"Right," Pecker responded.

"Nothing wrong about that?" Bove asked.

"No," Pecker responded.