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 National Enquirer publisher David Pecker testified that he believed Donald Trump had knowledge about the $150,000 contract to buy Karen McDougal's silence regarding an alleged year-long affair.

"Do you know if anyone else besides Michael Cohen had any knowledge of this contract?" prosecutor Joshua Steinglass asked.

"Yes, I believe Donald Trump did," Pecker responded.

"Was your principal purpose to suppress the story to prevent it from influencing the election?" Steinglass asked.

"Yes," Pecker said.

"Were you aware that expenditures by corporations made for the purpose of influencing an election made in coordination with or at the request of a candidate or campaign were unlawful?" Steinglass asked.

Pecker said he was aware and confirmed that the Enquirer's parent company, AMI, never reported the payment to the Federal Election Commission.

"We purchased the story so it wouldn't be published by any other organization," Pecker said.

"Why did you not want it to be published by any other organization?" Steinglass asked.

"We didn't want the story to embarrass Mr. Trump or embarrass or hurt the campaign," Pecker said.

"Who is we?" Steinglass followed up.

"Myself and Michael Cohen," Pecker said.

According to Pecker, AMI agreed to the $150,000 payment on the promise that Donald Trump or the Trump Organization would reimburse AMI for the payment. He frequently followed up with Cohen about the reimbursement and got a similar answer from Cohen.

"Why are you worried? I am your friend. The boss will take care of it," Pecker said about Cohen's response.