From convicted fraudster to convicted murderer.

Deadbeat Massachusetts dad Brian Walshe will spend the rest of his life behind bars for killing the mother of his three children — though the exact circumstances of her 2023 death may forever remain a mystery.

Walshe, 50, showed no emotion as jurors said they found him guilty of murdering Ana Walshe, 39, sometime around New Year’s Day following a boozy evening with a pal at their home.

The 12 jurors didn’t buy Brian’s bizarre explanation that Ana simply died in her sleep after hearing two weeks of testimony that their marriage was on the rocks, strained by the hubby’s fraud conviction for peddling fake Andy Warhol paintings that left him more than $475,000 in debt.

He now faces a mandatory sentence of life imprisonment without the possibility of parole for his first-degree murder conviction — and another 20 years for lying to cops and three years after admitting to getting rid of her body.

Ana’s remains were never recovered but prosecutors said they were incinerated after Brian stuffed them in trash bags.

Jurors deliberated nearly six hours over Friday and into Monday.

Brian — who has been in jail since his arrest — was handcuffed and shackled before he was escorted out of the courtroom.

Norfolk County District Attorney Michael Morrissey told reporters during a press conference later Monday that it’s rare to secure a conviction on first-degree murder without having recovered a body.

Morrissey’s prosecutors “put on a very great case in a difficult setting,” he said.

“We have seen other cases where we didn’t have a body, but this is the first one I can remember where we have had a first-degree murder conviction.”

Morrissey said he spoke with Ana’s sister who said, “Justice has been served.”

“Let’s remember Ana’s three young children who will be without a mother and especially at this difficult time of year,” Morrissey said. “We all wish them a great future going ahead.”

Greg Connor, the trial prosecutor, said he believed nailed the conviction despite the lack of direct evidence because of police work that left no stone unturned.

“What we had was a very thorough investigation that gave the lawyers in this case an excellent chance to try to give the jury what they needed,” Connor said.

Prosecutors argued that Brian killed Ana after he found out she was cheating on him with another man, the breaking point for their already strained marriage owing to the financial and emotional toll Brian’s federal art fraud conviction had taken on the family.

But Brian’s defense team claimed he didn’t know that Ana was having an affair and wasn’t the jealous type.

Instead, they alleged that Ana died after New Year’s festivities at their Cohasset, Mass., home of “sudden unexplained death” and Brian, fearing he’d be blamed, sought to cover it all up.

Prosecutor Anne Yas, during closing arguments Friday, said the defense’s theory that she died of natural causes “defies common sense.”

Before trial, Brian pleaded guilty to one count of lying to the cops and one count of disposing of Ana’s body after dismembering it and disposing of it in dumpsters. But he denied he murdered her.

Prosecutors say Brian carried out a slew of alarming web searches in the hours and days after Ana’s death, including looking up how to dismember a body, searching how long DNA lasts, and even researching serial killer Patrick Kearny, who earned the nickname the “Trash Bag Killer” for putting his victims’ remains in trash bags.

He then went to a handful of stores in Massachusetts, like Home Depot, Lowe’s and Walmart, where he picked up tools and cleaning supplies for his grisly task of taking Ana’s body apart, prosecutors allege.

Jurors saw video of Brian by the dumpster near his mom’s home, where investigators recovered a Tyvek suit, pieces of a bloodstained rug, a hatchet, hacksaw and other items that experts testified had Ana’s DNA on them. The panelists were also shown photos of the items retrieved from the trash.

The jury also heard from three key witnesses, including William Fastow, the man with whom Ana had a romance.

Fastow told jurors Ana was “despondent” that she wasn’t more involved with her kids as she was living and working in Washington, DC, and traveling back and forth to Massachusetts on the weekends to be with Brian and their three sons.

Brian was stuck in the Bay State under house arrest because of the criminal fraud case for which he owed nearly $500,000 in restitution and was facing prison time. He couldn’t move to DC with the boys to join Ana, jurors learned.

Two other close friends of Ana testified Wednesday about how she was unhappy about being apart from her kids and their family being in a state of limbo until Brian was sentenced.

Best friend Alissa Kirby said when she saw Ana just a few days before her disappearance, “she was really hitting a breaking point.”

“She really wanted to be with her kids, their marriage had been really strained for a long time,” Kirby said of Ana.

And Ana wanted Brian to “take responsibility” for his crimes, even if it meant he would get prison time, because Ana wanted him to get it over with so the family could live together again, Kirby testified.

Kirby said Ana also confided in her that she hadn’t slept with Brian in over a year because of the pressure they were under.

Walshe family friend Gem Mutlu testified that Brian told him on New Year’s Eve that he’d only made around $50,000 or $60,000 that year while Ana made $300,000 with her bonuses. And Ana told Mutlu on a call a few days prior that it was difficult for her to spend so much time away from her kids.

Brian didn’t testify in his own defense and his team didn’t call any witnesses or offer any evidence.

Experts said they weren’t surprised by the outcome of the trial given the “tidal wave of circumstantial evidence” against Brian and the total lack of a defense case.

“It’s unique to have a circumstantial, no-body case with this much evidence,” criminal defense attorney John W. Day said.

“The direct evidence that Walshe murdered his wife doesn’t exist, but prosecutors unleashed a tidal wave of circumstantial evidence and that’s what sank him.”

Day said since prosecutors didn’t offer a plea deal Brian was forced to “roll the dice” at trial.

“The defense didn’t have any great cards to play in this trial,” Day said. “This is not a whodunit.”

Another criminal defense attorney and former prosecutor Neama Rahmani said the defense had no case and he’s shocked the jury took so long to convict Walshe.

“The only surprise is that it took the jurors more than a single hour to return a guilty verdict,” Rahmani said. “This verdict was inevitable from the very beginning, it’s what we call a ‘slow guilty plea.’”

Rahmani said if Brian had testified, he “would have been torn to shreds during cross-examination” by prosecutors because his natural-causes defense “made no sense.”

Brian’s lawyers didn’t return requests for comment Monday afternoon.