Prosecuting a murder case without a victim's body is possible but a "difficult task" because there "must be sufficient evidence to show that the alleged victim is indeed dead," a Massachusets criminal defense lawyer said.

Sixteen days have passed since Ana Walshe was last seen during a New Year's celebration at her Cohasset, Massachusetts home, and there's still no sign of her or her body.

But speculation that she's been killed has intensified as the weeks pass without answers, and Walshe's friends have told Fox News Digital they believe the chances of finding her alive is "grim."

Nathaniel Amendola, a criminal defense lawyer in Massachusetts who's been following the case closely, said in a post on his website that prosecutors can rely on other types of evidence to show that a death has occurred. 

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"A confession, for example, may help satisfy that burden, though the law requires that some additional evidence corroborates the confession," Amendola wrote. "As of right now, there’s no direct evidence that Ana Walshe is dead. But there may be some circumstantial evidence that she is."

He said, for example, if the blood found in the basement of the Walshes' home, as well as a broken knife, is positively identified as Ana's, "one can infer that it got there because she was cut by the knife."

"If the authorities can piece enough of this type of evidence together, they may be able to show, circumstantially, that Ana is dead," Amendola said.

That's what Daniel Bibb, a former Manhattan assistant district attorney-turned criminal defense lawyer, had to do when he prosecuted Dr. Robert Bierenbaum for the 1985 murder of his wife, Gail Katz.

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Bibb called it "the toughest case of our career" when he spoke to Fox News Digital last August about prosecuting a homicide when the victim's body has not been found. He weighed in on the challenges of that type of case amid last summer's trial in Kristin Smart's disappearance, which led to Paul Flores being convicted of murder.

"There were two aspects to building this case," Bibb said about the Katz case. "The first was, can we prove that she is deceased? And looking at all evidence – not only the evidence as it existed then, but the evidence that was developed. There are two issues here: Is she dead, and who killed her?

"The problem was, could we prove it beyond a reasonable doubt? And when we were done investigating and we … sat down and went over it piece-by-piece, we came to the conclusion that she was dead, and he did it."

Bibb and his team secured a conviction against Bierenbaum in October 2000, and 20 years later, Bierenbaum confessed to the murder during a parole board hearing. 

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Brian Walshe was arrested for allegedly lying to police about his whereabouts on Jan. 1 and Jan. 2 while police were searching for his wife, according to the probable cause affidavit for his arrest.

Law enforcement and the Norfolk District Attorney's Office, which is prosecuting Brian Walshe's case, haven't publicly named Ana's husband as a suspect or person of interest. 

It took three days for anyone to report Ana Walshe missing, according to authorities. 

Search warrants were executed last Thursday and then impounded, which means they were returned and not available to the public, a member of the Quincy District Court told Fox News Digital.

There's no plan to unseal them, the court said last week, so it's not yet known where the warrants were executed and what was recovered. 

In the days between Ana’s disappearance and the missing person’s report, Brian Walshe allegedly lied about his own whereabouts. Investigators said Walshe told investigators he traveled to stores, such as CVS and Whole Foods, where he might not have actually been.

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But he allegedly neglected to mention that he spent about $450 in cash buying cleaning supplies from a Rockland, Massachusetts, Home Depot. 

Investigators also discovered blood and a bloody, damaged knife in the basement of the couple’s home, prosecutors said. Police also reportedly found bloody trash bags, a hatchet and a hacksaw at a waste facility about an hour from the family's home.

They also traced Ana’s cellphone to the area of the family’s Cohasset home on Jan. 1, and approximately 0.7 miles away from the home on Jan. 2, according to officials and a police log. 

Brian’s cellphone pinged in other parts of Massachusetts, such as Brockton and Abington, despite his lack of permission to be in the areas under the terms of his home confinement. The convicted art swindler was under home confinement as he awaits sentencing for selling bogus Andy Warhol paintings.

Officials previously revealed that investigators recovered evidence when they appeared to have removed — and then replaced — a dumpster taken from Brian Walshe's mother's Swampscott home, located nearly 35 miles from the couple's home. 

And a recent CNN report described how Walshe had conducted internet searches for "how to dispose of a 115-pound woman's body" and how to dismember a body.

Brian Walshe was arrested on Jan. 8 and charged with misleading a police investigation. 

Police said the charge stemmed from Walshe's alleged "intentional, willful and direct responses to questions about his whereabouts on the days of Sunday, January 1, 2023 and Monday, January 2, 2023." 

They further called it, "a clear attempt to mislead and delay investigators."