The undated "burn after reading" letter from Brian Laundrie's mother could provide what one legal analyst called the "proverbial smoking gun" in the civil case brought by Gabby Petito's family against his parents.

But the note, recovered from Laundrie's backpack after his remains were found in October 2021, is unlikely to expose Roberta Laundrie to criminal charges in connection with Petito's death at the hands of her son, according to legal experts.

"It would be very difficult to embroil her into an accessory-after-the-fact type of crime when she hasn't taken any substantial step towards the commission of that crime," CNN legal analyst Joey Jackson said of Laundrie's mother. "So I would be on the side of no criminal exposure whatsoever."

Elie Honig, a CNN senior legal analyst, said the letter alone is not "conclusive evidence" of a crime.

"No prosecutor would bring criminal charges based solely on this letter," said Honig, a former federal and state prosecutor. "But the letter could be useful evidence in the bigger picture towards building a case potentially for obstruction or accessory after the fact."

He added, "You can't just point at that letter and go, 'Smoking gun. Where's the indictment?' But I think if there's other evidence showing that there was some genuine effort by one of the parents or both of the parents to help him evade the law or to help him obstruct justice ... this letter would absolutely be an exhibit in that case."

And the letter could be useful to the Petitos in the civil trial, according to Honig.

The letter was the subject of arguments in a Sarasota County, Florida, courtroom on Wednesday, with attorneys wrangling about the note's relevance to the lawsuit brought by Petito's parents against Laundrie's parents and the Laundries' former attorney.

The Petitos sued the Laundries for emotional distress in connection with Petito's death. She was killed while traveling in the western United States with Brian Laundrie, her fiancé. Laundrie returned home from the trip without Petito and disappeared several weeks later.

Petito's remains were found at Wyoming's Bridger-Teton National Forest in September 2021 and her death was ruled a homicide by manual strangulation. Before taking his own life, Brian Laundrie wrote in a notebook he was responsible for her death, according to the FBI.

Roberta Laundrie says letter was written before fateful trip

The Petito family argues that Laundrie's parents and their attorney knew that Petito had been murdered and knew the location of her body when the Laundries issued a statement on September 14, 2021, about the search for her. The statement at the crux of the civil case said, in part, "It is our hope that the search for Miss Petito is successful, and that Miss Petito is reunited with her family."

Jackson said the "burn after reading" reference helps support the Petito family argument that Laundrie's parents "knew the wrong your son did and you were completely prepared to cover it up."

"And with all that knowledge you had about your son killing our daughter and our daughter no longer being on this earth, you still decided to come up with that statement," said Jackson, a defense attorney. "So the 'burn after reading' is going to be argued by the Petito family as the proverbial smoking gun that they knew."

In the letter, Roberta Laundrie wrote that she would "bake a cake with a file in it" to help her son in jail, according to a copy of the undated note obtained by CNN.

"I just want you to remember I will always Love you and I know you will always Love me. You are my boy. Nothing can make me stop loving you, nothing will or could ever divide us. No matter what we do, or where we go or what we say- we will always Love each other," Roberta Laundrie wrote in the letter.

"If you're in jail I will bake a cake with a file in it. If you need to dispose of a body I will bring show up with a shovel and garbage bags," the letter said, with an apparent cross out over the word bring. "If you fly to the moon, I will be watching the skies for your re-entry. If you say you hate my guts, I'll get new guts."

Roberta Laundrie said in court documents the letter was written before her son's trip with Petito, and one of her attorneys released a statement saying it was "in no way related to Gabby," although Petito's family has challenged those assertions.

The letter also quotes from Romans in the Bible.

"Nothing can separate us; not hatred, not hunger, not homelessness, not threats, not even sin, not the thinkable or unthinkable can get between us," it reads.

The envelope containing the letter said "burn after reading" and was recovered from Brian Laundrie's backpack when his remains were found in October 2021.

Roberta Laundrie, in a court filing, said the language in the letter was meant to "describe the depth of a mother's love" and was inspired by two books -- "The Runaway Bunny" and "Little Bear."

She also said the "burn after reading" reference was based on a book called "Burn After Writing" that Gabby Petito had gifted her son.

'A mom ... will say, frame after reading'

"They're going to say in the event that this was a simple expression of a mother's love -- we'll say the Petitos -- why on earth would a mom say, 'burn after reading?' A mom, if it's an expression of love, will say, frame after reading, so that you can always be reminded of my love for you and my support of you and what I'll do for you," Jackson said.

In a statement Thursday from Roberta Laundrie's attorney, Steven Bertolino, she encouraged people to read the letter in its entirety.

"I truly loved my son, and simply wanted to convey to him how much he meant to me and how much I loved him," she said.

"I am sure people use phrases all the time to express to their loved ones the depths of their love. Although I chose words that I thought would be impactful with Brian given our relationship, the letter was in no way related to Gabby," she added.

"I ask that you read it in its entirety, and understand that the letter contains other phrases besides those highlighted by Pat Reilly for sensationalism and to bolster his case," she said, referring to the Petito family attorney.

She has made similar assertions in court documents, saying the letter was meant "to reach out to Brian while he and I were experiencing a difficult period in our relationship."

Prosecutors hard-pressed to prove criminal charges against mother

In court, Petito family attorney Patrick Reilly argued the letter was important in their lawsuit against the Laundrie family.

"As we all know, the letter references burying a body, bringing a shovel and burying a body," he said. "Those are criminal acts, by the way, that Roberta Laundrie has said she would commit."

But Alfredo Garcia, a law professor at St. Thomas University College of Law in Florida, said prosecutors would be hard-pressed to prove criminal charges against Laundrie's mother beyond a reasonable doubt.

"It might be a difficult climb for the prosecution to establish guilt under an accessory after the fact statute given the burden of proof," Garcia said via email from Spain, where he is teaching. "That is, to prove she knew he committed a homicide and intended to assist him in evading apprehension, trial, conviction or punishment."

It's unclear whether Roberta Laundrie is the subject of a criminal investigation. A spokesperson for the local prosecutor's office said she couldn't confirm, deny or comment. CNN has sought comment from the FBI and North Port City Police Department.

The Petito family said Laundrie's statement about the letter this week is "self serving."

"The letter is undated, and while Roberta Laundrie has suggested it was written before Brian Laundrie and Gabby Petito left on their trip, a reasonable inference is that it was written after Gabby Petito was murdered, and is evidence that the Laundries and Attorney Bertolino were aware of Gabby Petito's demise when the statement at issue was released on September 14, 2021," the Petito family said.

"We look forward to having a jury determine when the letter was written at the time of trial," the Petito family added.

While the letter is unlikely to result in criminal charges against Laundrie's mother, Jackson said, the note could prove critical to the Petitos in the civil trial.

"You engaged, is the allegation by the Petito family, in outrageous behavior. You knew, is the allegation, that our daughter was dead, but yet you put out this letter expressing you hope she's found safe. That was harmful. It was outrageous. It was beyond the pale of human decency, if you knew," Jackson said.

"In the civil context, it is relevant ... because what I have to prove now is that you engaged in outrageous conduct because you are aware our daughter was dead, and you came up with some statement to give us false hope. And that was just totally indecent."