"I thought, ‘Oh man, here is a guy who has written a book about forgiveness, has taught about this,’” Worthington said of himself. Surely, he thought, an expert on forgiveness could find a way to make peace with even the most heinous perpetrator.

He decided he was going to try to forgive the killer.

Mind you, Worthington does not forgive easily. He says he once had a professor who gave him a B and it took him “10 years and a religious experience to forgive that guy.” But he knew from his research that carrying around the anger over his mother’s homicide would be worse than the painful process of absolution.

To do it, Worthington used his own, five-step “REACH” method of forgiveness. First, you “recall” the incident, including all the hurt. “Empathize” with the person who wronged you. Then, you give them the “altruistic gift” of forgiveness, maybe by recalling how good it felt to be forgiven by someone you yourself have wronged. Next, “commit” yourself to forgive publicly by telling a friend or the person you’re forgiving. Finally, “hold” onto forgiveness. Even when feelings of anger surface, remind yourself that you’ve already forgiven.

What helped on the empathy front, Worthington says, was that after the intruder killed McNeill, he ran from room to room, smashing all of the mirrors with the crowbar—even in the rooms he didn’t search. Worthington took it as a sign that he couldn’t look at himself.

“I started thinking about this from the point of view of someone who is keyed up and think they have perfect crime, and this woman is looking at them right in the face, and he has the means right in his hand,” Worthington said. (It’s worth noting that no one has been convicted in the murder, and the case against the leading suspect was dropped. I’m using male pronouns, but this might have been a woman.)

After that first, agonizing 24 hours following his mother’s death came another 20 or so during which Worthington says he went through all five REACH steps. He forgave his mother’s murderer completely. He says it was important to do so right away.

“I was emotionally aroused, and that magnified all the emotional experiences I was having,” he said. “So when I had the experience of working through and forgiving this person, it gave it a little extra power. If I had done it two days later, when I was calmed down, probably it wouldn't have had as much effect.”

Talking about the “benefits of forgiveness” can feel slightly self-serving, like donating to charity only so you can tell people about it later. But one reason why people might avoid forgiving is that it feels like the offender gets away with something—especially if he or she never apologized. In that sense, at least, it’s worth considering what’s in it for the forgiver. And as it turns out, there’s a lot.

First, there’s a sizable and immediate mental-health boost. Worthington says that an eight-hour forgiveness workshop can reduce subjects’ depression and anxiety levels as much as several months of psychotherapy would.