In March, Eric McLean shot and killed Sean Powell, an 18-year-old former student of McLean's wife, Erin. 

The events leading up to the murder begin with a seemingly calm Eric McLean calling 911 to report an intruder.

911 operator: Do you know this person?
Eric McLean: Yes.
911 operator: Ok, who is it?
Eric McLean: Some guy who's stalking my wife.

Prosecutors and the defense agree on one major point. There was a crucial seven minute interval between Eric McLean's phone call to 911 and the shot that killed Sean Powell. It's these critical seven minutes that could end up deciding the case -- and Eric McLean's fate.

Some observers say Erin McLean's testimony about the night of the shooting will hold the key to what happens to her husband. Jamie Satterfield has been covering the story for the Knoxville News Sentinel.

Jamie Satterfield: Did she taunt him?  Did she tell him, "There's no way, you know, I'm ever going to reconcile with you, and we're going to move to Tahiti with the kids and bye-bye," and then he went nuts? 

Whatever happened, Erin McLean has not been charged with any wrong-doing.

She declined Dateline's request for an interview, but her attorney, Gary Blackburn, shared some information about her version of events, beginning with her take on life with Eric.

Blackburn: There was no marriage. Erin and Eric rarely saw each other.  Erin worked a full shift after being in class during the day, and then was in a band. Would come home routinely at three in the morning. The two of them had a classic loveless marriage.

Blackburn says that Erin's loneliness, coupled with the compassion she felt for Sean's troubles at home and school, were a powerful combination.

Gary Blackburn: He was a very, very troubled young man and very bright. And she knew these things and felt sorry for him … And she was lonely.  Extremely lonely.  And very vulnerable to the attentions of a young man who shared her interests and seemed interested in her. 

Blackburn says the sexual relationship only began months after Sean Powell was expelled from West High. But then, by last winter, Sean Powell became a regular visitor to the McLean home.

Blackburn: Over a period of time, it became an intolerable situation …  as it inevitably would have.

As for what went on during the seven minute gap between 911 calls, Blackburn says Erin doesn't know that much because she was in the house when the fatal shot ran out.

Gary Blackburn: Sean made provocative statements of some kind to Eric … Remember -- Erin was in the house.  Sean was in his car.  The only one out there on foot holding a weapon was the man who's under indictment.

Blackburn says Erin heard the shot and then ran outside.

Gary Blackburn: Erin came outdoors and saw Eric standing there behind the vehicle, holding the rifle. And he looked at her and said, "Congratulations."

Erin McLean's attorney paints a far different portrait of the McLean marriage than Eric does.

Blackburn provided Dateline with letters and cards from Eric, written before the shooting, that appear to show he was abusive to her. "I love you and I'm sorry for the way I've mistreated you," one says. "Please forgive me in time."

Through her attorney, she claims Eric abused alcohol and had psychological problems. Erin denies Eric's claims that she was drinking heavily or abused him.

And her attorney strongly denies Erin ever neglected or abused their children.

Gary Blackburn [Erin McLean's attorney]: The notion that Erin McLean abused her children is completely false.  The Tennessee Department of Children's Services has been here to Nashville, have interviewed the boys privately, and have closed any investigation.

Erin McLean and her two boys are still living in the Nashville area.  

Her attorney says she deserves a second chance.

Gary Blackburn: Erin very much regrets everything that's happened.  She understands that she's made some mistakes.  She's made some bad choices.  All of us passing through this world make mistakes and make bad choices.  Usually, we get through them without a major tragedy.  She did not.

Sean Powell's birth mother, Debra Flynn, says it will be difficult to ever forgive Erin McLean.

Debra Flynn: I said, "You preyed on my son," and she said, "No I didn't, I loved him.  He asked me to marry him, and I was going to marry him."

Marry him? Erin McLean isn't talking. But Debra Flynn reserves her deepest anger for the man who fired the gun: Eric McLean.

Debra Flynn: Sean was defenseless.  He murdered my son, execution style, flat out. The detective said he had never seen that much brain matter in his life. I couldn't kiss my son goodbye.
Natalie Morales: You wanted to kiss him goodbye?
Debra Flynn: Yes, and I couldn't because he had no face.

Friends, meanwhile, are still stunned.

Tamara Mulkey: We never, never could have imagined that anything like this could have happened.

Natalie Morales: I see you're still wearing your wedding band.  Why?
Eric McLean: I still love her, but I know we can't be together anymore.  You know?
Natalie Morales: You do still love her, though?  After all of this?
Eric McLean: Well, I just can't talk to her anymore … She's just not the person I thought she was.  You know?  So it seems like I've been in love with somebody who doesn't even exist anyway.

It appears the marriage itself may not exist much longer: In the past week, Eric McLean's lawyer told us that Eric is planning to file for divorce from Erin.