(CNN) — A federal judge on Monday is scheduled to sentence Alex Murdaugh – the 55-year-old former attorney already serving two life sentences for the murders of his wife and son – for nearly two dozen financial crimes following his guilty plea last year, according to the US Department of Justice.

What should have been a straightforward sentencing hearing, however, could be complicated by prosecutors’ allegation in a motion last week that Murdaugh failed a polygraph test, violating the terms of a plea agreement that required his honesty. Murdaugh denies the claim, and his attorneys asked the judge to disregard the government’s motion during sentencing Monday.

Murdaugh pleaded guilty last September to 22 federal charges, including conspiracy to commit wire fraud and bank fraud, wire fraud, bank fraud and money laundering after federal prosecutors accused him of defrauding his personal injury clients and namesake law firm of millions of dollars in settlement funds he used for his personal benefit.

Each charge carries a maximum sentence of up to 20 or 30 years, the US Attorney’s Office for the District of South Carolina said previously. In a filing last week, prosecutors recommended Murdaugh be sentenced to between 17.5 and almost 22 years in prison.

The now-disbarred attorney was previously sentenced in state court to 27 years for similar crimes after pleading guilty to almost two dozen charges including money laundering, breach of trust, conspiracy, forgery and tax evasion. That’s in addition to the consecutive life sentences he received a year ago for his conviction of the June 2021 murders of his wife, Maggie, and 22-year-old son, Paul – killings state prosecutors cast as a desperate attempt to distract from and delay investigations into his unraveling financial schemes.

While Murdaugh insists he is innocent of the murders, he has admitted to the financial crimes, saying he was maintaining a yearslong opioid addiction.

Whether the federal sentence imposed Monday is served concurrent with Murdaugh’s state sentence depends on whether a federal judge determines – as prosecutors alleged – he breached his plea agreement by failing a polygraph test.

In exchange for his guilty plea, federal prosecutors agreed to recommend Murdaugh’s sentence be served concurrently with the one imposed in South Carolina, court filings show. But in light of the failed polygraph test, prosecutors asked the judge to release the government from the terms of the plea deal, freeing them from the obligation to recommend a concurrent sentence.

At the same time, prosecutors proposed a motion to seal the polygraph examination report and four FBI reports about interviews with Murdaugh last year, saying all are related to an ongoing grand jury investigation and allegations of criminal activity by other people.

Murdaugh agreed to the polygraph examination as part of his plea deal – which explicitly required him to be “fully truthful and forthright” – as officials work to recover the millions of dollars he bilked from his victims.

What exactly Murdaugh was asked and how he responded is not publicly known, though the government’s filing indicates the examination was conducted “on issues related to hidden assets and the involvement of another attorney in Murdaugh’s criminal conduct.” But the results of a two-part polygraph test in October 2023 indicated deception, the government claims, voiding the agreement.

Murdaugh’s attorneys have asked the judge to either deny or delay ruling to hold their client in breach of the plea agreement until the polygraphs are provided to him, according to their own sentencing memorandum Thursday.

They claimed the polygraph examiner engaged in “odd conduct” to manipulate the results in a way that would void the plea agreement. That included allegedly sharing his belief Murdaugh is innocent of his wife’s and son’s murders, their filing said, and “‘secretly’ confiding” to Murdaugh he had just performed a polygraph on Joran Van der Sloot, who confessed last year to killing Natalee Holloway almost two decades ago.

Ultimately, Murdaugh’s attorneys contend the government’s conduct prior to the polygraph exam and the agent’s conduct during it “raises significant concerns as to whether the Government has acted in good faith.”

Murdaugh’s attorneys also opposed the government’s motion to seal the evidence, arguing prosecutors had not adequately explained why a “less drastic” action, like redactions, would not be sufficient.

US District Court Judge Richard M. Gergel on Friday ordered prosecutors to file a redacted version of those documents, adding the court understood why the government wanted to keep them sealed: A “detailed explanation” to justify the sealing could undermine the ongoing investigation, the judge wrote.

However, Gergel also indicated it was possible for sentencing to proceed Monday without divulging details from the documents the government wants to keep under seal.

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