A criminal trial was approaching for the man accused of killing Ben Mogen’s daughter, Maddie, and three of her friends at the University of Idaho. Then, last week, Mr. Mogen logged on to a Zoom call to find a group of prosecutors waiting to talk to him.

The conversation covered logistics of the trial and how families of the victims would be able to leave the courtroom when potentially painful evidence was presented. There would be many such moments, the prosecutors warned, with horrific details and images of the crime scene to be shown as evidence.

As the call wrapped up, the prosecutors asked Mr. Mogen a final question: How would he feel if they were able to reach an agreement with the defendant, Bryan Kohberger, to enter a guilty plea?

Mr. Mogen, recalling the conversation, said he talked about how the case had been tormenting him and his family. They wanted to heal. They were dreading a trial. “It’s been this nightmare that’s approaching in our heads,” he told them.

Just a few days later, a plea deal emerged, with prosecutors agreeing to take the death penalty off the table in exchange for an admission of guilt and a lifelong prison sentence for the defendant. In it, Mr. Kohberger, 30, a criminology student at a nearby university at the time of the murders, agreed to plead guilty to fatally stabbing the four students at a home near their campus in Moscow, Idaho.

It was a stunning turn in the case, and it followed more than two and a half years of legal battles between prosecutors and defense lawyers as they prepared for a trial in August. It also came over the objection of family members of at least two victims, with one family urging the judge to take the rare move of rejecting the deal.