A 30-year-old man who is due to stand trial for the fatal stabbings of four roommates in 2022 in a small Idaho college town is expected to plead guilty as part of a deal to avoid the death penalty, according to US media.

The agreement was revealed in a letter sent to the victims' families, parts of which were seen by the BBC's US partner CBS News.

Relatives of one victim, Kaylee Goncalves, appeared to confirm the agreement. "It's true! We are beyond furious at the State of Idaho," they wrote in a social media post. "They have failed us."

Ms Goncalves, Ethan Chapin, Xana Kernodle and Madison Mogen were killed in their off-campus home in the city of Moscow, days before Thanksgiving in 2022.

The attacks shocked the nation.

Bryan Kohberger, who was a graduate criminology student at nearby Washington State University, is currently due to stand trial in August. He has so far contested the charges, and prosecutors are yet to allege a motive on his part.

The letter that was sent to the victims' families by prosecutors was shown to CBS by Ben Mogen, the father of Ms Mogen. The Latah County prosecutor's office earlier refused to directly confirm to the BBC that a deal had been reached.

Mr Mogen told CBS that he felt that the agreement represented "justice". He said drawn-out discussions involving the death penalty would have meant continued "torture" for families who had already gone through "the most horrific thing they could ever imagine".

Under the alleged deal, Mr Kohberger is expected to plead guilty on all four murder charges and waive his rights to any future appeals.

A hearing for the plea deal has reportedly been set for Wednesday. The BBC has contacted the defendant's legal team for comment.

If accepted by a judge, the deal would reportedly see the defendant sentenced to life in prison without the possibility of parole. Prosecutors would not seek capital punishment.

"We cannot fathom the toll that this case has taken on your family," Moscow Prosecuting Attorney Bill Thompson told families in the letter, according to the Idaho Statesman newspaper - which reported that it, too, had seen a copy.

"This resolution is our sincere attempt to seek justice for your family.

"This agreement ensures that the defendant will be convicted, will spend the rest of his life in prison, and will not be able to put you and the other families through the uncertainty of decades of post-conviction appeals."

The defendant was arrested at his Pennsylvania family home weeks following the stabbings, after investigators said they found DNA evidence on a "leather knife sheath" at the crime scene. He was indicted by a grand jury in May 2023.

Court documents revealed police recovered a knife, a Glock pistol, black gloves, a black hat and a black face mask during a search of Mr Kohberger's family home.

His defence team questioned the accuracy of the DNA evidence and succeeded in its bid to move the trial location, after arguing their client would not receive a fair hearing from local jurors.

But they had failed to remove the death penalty as a sentencing option, after citing an autism diagnosis for Mr Kohberger.

Idaho is one of 27 US states that allows for capital punishment, but there have been no executions since 2012, according to a database by the Death Penalty Information Center.