Produced by Taigi Smith and Gail Abbott Zimmerman

Art Gonzales to 911: My wife just attacked me with a knife and I had to shoot her.

Soon after FBI Special Agent Art Gonzales' frantic 911 call on April 19, 2013, reporting that he'd shot his estranged wife, Julie, police in Stafford, Virginia, were sizing him up.

FBI agent shoots estranged wife; calls 911 00:59



"By the time I got there, I had already heard that he was an FBI agent," Detective Todd Nosal told "48 Hours" correspondent Susan Spencer. "I knew going into this that he would be well aware of what his rights would be."

To Detective Nosal's relief, Gonzales was willing to talk -- and without a lawyer.

Gonzales said he'd taken the day off, had lunch with a friend, and gone home. To his shock, Julie was there:

Art Gonzales to Det. Nosal: So I got there, I was completely surprised that she was there. I'm like what the f--- is she doing here.

Julie said she'd come to pick up some clothes - she'd moved out six months earlier, after Art filed for divorce. She had willingly given him custody of the kids for now, but the couple was still in contentious negotiations and things were moving very slowly.

Art Gonzales to Det. Nosal: I said we need to talk about what's going on with the divorce since you're here ... Essentially it's over. We need to complete this process.

"He basically says that, 'I don't love you anymore,' as they're standing in the kitchen. And then she launches -- a knife attack," said Det. Nosal.

"That's a mean looking knife," Spencer commented to the detective, as he held the knife.

"It's intimidating," he said.

Paramedics found Julie Gonzales on the floor with this knife in her hand Commonwealth of Virginia

Art Gonzales to Det. Nosal: She attacked me, she came at me... I put up my arm... she came back at me again.

"And then he said he just reacted," said Det. Nosal.

Art Gonzales to Det. Nosal: I just reacted, and ... shot. That's really the extent of what happened.

"Is there anything ... that makes you say, 'Wait a minute?'" Spencer asked Det. Nosal.

"No, no," he replied.

"It's a perfectly plausible explanation," Spencer noted.

"Right," Det. Nosal said. "Estranged wife in the home, knife in the wife's hands ... Yeah, on face value ... it could possibly be that."

"He seemed upset. When I told him that Julie Gonzales was dead," the detective continued. "He sobbed."

With four bullets pumped into her chest from Art's FBI-issued gun, Julie never had a chance. Her parents, Rey and Maryetta Serna, were both heartbroken and bewildered.

"I couldn't comprehend," Rey Serna said. "Why would he do that? ...They weren't even living together."

"She picked up a knife, and lunged for him, came at him?" Spencer asked. "Why is that impossible?"

"Because that wasn't her character. That's not who she was," said Rey Serna.

"Julie was a gentle lady that wouldn't even hurt -- a fly," he continued.

The Sernas remember the little girl who grew up in Soccoro, New Mexico, who got along with everyone -- always active and confident.

"She would tackle anything in the world. And she'd be successful at it. She could do anything," Julie's proud father said.

Julie and Art Gonzales on their wedding day Serna family



Julie was in her high school's homecoming court. She went to college in northern New Mexico and, in 1995, married her college sweetheart, Art Gonzales, who later joined the FBI as a field agent in California.

"He became one of the family," Rey Serna told Spencer. "...we saw him as ... almost a son."

Art Gonzales next became an FBI agent in Texas before rising to supervisor in the Las Cruces, New Mexico, field office in 2005. The couple had two boys, and then in 2010, they moved to Stafford, Virginia, after Art received a promotion to teach ethics at the FBI Academy.

His supervisor, Doug Merel, became a close friend -- as did Doug's wife, Jen.

"A person comes into the bureau ... to serve the public," Doug Merel said. "I saw he had the same motivation, dedication, compassion, and abilities that I had. ...And Art was one of the good ones."

Meanwhile, Julie had taken a job as a teller at a local bank. The Merels both had reservations about her.

"Julie was troubled," said Jen Merel.

"And was that apparent to you from the first time you met her?" Spencer asked.

"Yes," she replied.

"In what way?"

"She had some substance abuse. And you could tell," Jen Merel replied.

Doug Merel says the shooting was tragic for everyone involved.

"My first thoughts were, my goodness, this is the worst thing that I've ever could encounter for a friend and their family,'" he said.

Yes, he insists Gonzales did exactly what the FBI trained him to do.

"We don't shoot to kill, we shoot to eliminate a threat," Doug Merel explained.

"Four bullets was not excessive, in fact, it was restrictive. Agents are trained to shoot more bullets and then assess the situation," he continued.

"So you think if you would've been in the same situation, you would've done the same thing?" Spencer asked.

"Yeah, I believe if someone was trying to kill me," Merel replied.

"Not someone. Jennifer," Spencer pressed.

"If my wife was trying to kill me, and I could not do anything else, and I had to use deadly force, I would've had to. And I've have to live with that for the rest of my life," Merel replied, his wife at his side.

When Art Gonzales explained why he shot Julie he was succinct -- both on the 911 call -- "She just attacked me with a knife and I had to shoot her!" -- and with Detective Nosal: "I mean, I hadn't been there more than 10 minutes."

"...it was a very limited story without a lot of detail, the way he told it," said Det. Nosal.

Gonzales was far more expansive when it came to Julie's problems:

Art Gonzales to Det. Nosal: Four years ago, it was nightmarish. You know, she started drinking.

"He really bashed Julie Gonzales in that interview room," Det. Nosal said. "...it was all negative about Julie."

Art Gonzales questioned about his marriage 01:10



Especially her drinking:

Art Gonzales: I'd come home, have to make dinner. She'd be, you know, passed out on the couch. Det. Nosal: Was it beer, wine, liquor? Art Gonzales: Everything. Vodka.

While Art Gonzales was talking, police were searching his house.

"We had an incident where there were two people in the home. One of 'em's dead. And -- I'm getting one side of the story," said Det. Nosal.

What they found convinced the detective there might be more to the story than what Gonzales was letting on.

"...they found -- ladies ... panties ... in the master bedroom," said Det. Nosal.

Art Gonzales to Det. Nosal: It's a friend of mine that's been staying over every once in a while.

And a much more complicated explanation of how Julie Gonzales died.

"You think she didn't have the knife. You think she didn't attack him," Spencer noted to Det. Nosal. "You basically think this whole thing is made up."

"Yes," he replied.

A TROUBLED MARRIAGE

Before FBI agent Art Gonzales took his prestigious teaching job in Virginia, he and Julie lived a quiet life in Las Cruces, New Mexico.

The couple's two young sons kept Julie busy at home, except for a few months each fall, when she'd help out at a local Halloween store.

Julie Gonzales Donna Ulibarri

"She was beautiful and charismatic...people ... just loved her," said Julie's boss, Kim Scott.

"Her loyalty was incredible. I knew when I wasn't there, she had my back," said Scott.

"We talked about everything. We talked about our kids, we talked about our marriages, our family," co-worker Lea Lucero said. "She loved her boys. She was a great mother."

But Scott and Lucero were leery of Julie's husband, and they say he kept Julie on a very tight rein -- even monitoring the hours she worked.

"He just wasn't friendly," Lucero said. "He would call my cell phone repeatedly if he couldn't get a hold of her -- redial, redial, redial. And he would yell into the phone at me ... 'Where is Julie? Why isn't she home?' ... Interrogating me."

And he would show up at the store, often as many as four times a day.

"I wondered, 'What does he do as an FBI agent? What is his job that he has so much time to hang out here?'" said Lucero.

But what got her, Scott says, was Art's belittling of his own wife in front of their kids.

"We would hear him say things about her to the boys ... 'don't listen to your mother, she's stupid,'" she said. "He would tell them ... 'Your mom has no money. She's never going to amount to anything.'"

Art Gonzales Serna family

Art Gonzales refused "48 Hours"' repeated requests for an on-camera interview so he could tell his own story. Instead, he referred us to others to talk about his character. They agree that Gonzales was a devoted father, saddled with a wife who was drinking so much she wasn't even taking care of her own children.

"Her behavior was becoming a little bit more bizarre and strange and they were concerned 'cause that was their mother," Doug Merel said.

"I just saw her every time drinking too much," said Jen Merel.

"I never ever saw her drunk. I never saw her have more than one or two drinks at a time," said Lucero.

"I think anybody in her position would drink a lot more than she did. She was not an alcoholic," said Scott.

But Gonzales insists Julie had a drinking problem -- a point made repeatedly during the police interview just hours after the shooting:

Art Gonzales to Det. Nosal: She's absolutely volatile ... When she's drinking, she's impossible...

And he had photos to prove it: scores of pictures taken on his cell phone to document just how bad her drinking had become.

But by that point, the marriage was over.

Gonzales says Julie was so unstable that she'd almost attacked him with a knife once before:

Art Gonzales: She was cutting a tomato with a knife, and it was like she was about to come at me with a knife... then she threw tomato across the floor or across the room Det. Nosal: So you've got pictures of that then? Art Gonzales: ... I have a picture of the tomato.

Police searching his house were less interested in tomatoes than in what they found in Gonzales' bedroom: women's underwear and some mail.

"The name on the mail was Cara Kast," said Det. Nosal.

Det. Nosal: OK, I'm not the morality police. Like, are you guys hooking up? Art Gonzales: We're good friends.

They were very good friends. Gonzales captured a shot of Cara in bed on his cell phone just a few days before he shot Julie dead.

Det. Nosal: You guys having sex and stuff like that? Art Gonzales: Yeah.

"Cara Kast turns out to be ... an employee with the FBI," said Det. Nosal.

"What did you find out about this relationship?" Spencer asked.

"It was probably the worst kept secret at the FBI Academy," the detective replied.

Art Gonzales and Cara Kast Commonwealth of Virginia

Ironically, Gonzales was teaching that ethics class when their on-again off-again affair started around the time he filed for divorce. Detective Nosal found a rambling nine-page love letter in Gonzales' office.

"There's poems. There's quotes" Det. Nosal said. "I probably wasn't off the academy grounds before it had been referred to as 'the manifesto.'"

Art Gonzales had even picked a name for their future daughter.

"It has things in there such as him talkin' about dreams ... when they're together, what baby names they'll have if they have kids," the detective said. "We find ... there's a drawing of ... the love molecule."

Almost 36 hours before the shooting, while snooping through her phone, Gonzales found photos of Kast with another man.

"At 3:00 in the morning, he found pictures of Cara ... provocative shots," Det. Nosal explained. "In some of the shots ... was an FBI agent based in Indianapolis."

"Arthur Gonzales, bein' a guy who likes to be in control, has now found out that his 24-year-old girlfriend is seeing another agent," Det. Nosal continued. "That part of his life is spiralin' outta control."

"What is the FBI policy on having an affair with a coworker?" Spencer asked Doug Merel.

"The policy is very simple. Keep it out of the office," he replied.

But Doug Merel insists the shooting of Julie Gonzales had nothing to do with Art's obsession with Cara Kast and everything to do with the knife Art says Julie had.

"So when Art says, 'There was nothing I could do. I couldn't even say, 'Stop.' She was trying to kill me,'" Spencer read aloud to Doug Merel, he replied, "That's pretty self evident."

Not to Teresa Smith, a neighbor who was with Julie about an hour before she died.

"I invited her over to the house and ... she picked up some Chinese food for us and came over," she said.

Smith says she served not a drop of alcohol at lunch and, in fact, the autopsy found no trace of alcohol in Julie's system.

Smith also remembers her friend as upbeat that day. Saying the marriage was over and she was ready to move on, Julie had decided to spare the kids and not even fight for custody.

"She said, 'Well, I'm just gonna say this, and then that's the end of it,'" Smith told Spencer. "And she said, 'I've decided that I'm not gonna go after the boys. ... I'll just wait until they're ready to come see me.'"

"She was sad, but kind of looking forward to the future," said Smith.

It was not a picture of a distraught woman about to attack her ex-husband. Smith just didn't believe Gonzales' story for a minute.

"None of it makes sense," Smith said. "It sounds like something out of a textbook."

"He says it is out of a textbook," Spencer noted. "He says this is textbook training ...it just kicked in."

"That's not the textbook I'm talking about. I'm talking about the textbook that says this is how you investigate a murder," Smith said. "...this is how you set up the scene..."

Art Gonzales' booking photo Stafford County Sheriff's Office

The authorities agreed. Just three weeks after police marched him from the house where he shot his wife to death, Special Agent Arthur Gonzales was arrested and charged with murder.

And now, Stafford County Commonwealth Attorney Eric Olsen is determined to prove murder in the court of law. This case, says Olsen, was never about self-defense.

"The only evidence that Julie Gonzales came at Art Gonzales with a knife comes from Art Gonzales," said Olsen.

"Two worlds came together that day," he said, "and the result was the death of Julie Gonzales."

KILL OR BE KILLED?

In March 2014, one year after Art Gonzales shot and killed his estranged wife, Julie, the 18-year FBI veteran found himself on trial for her murder. No cameras were allowed in the courtroom.

"He used a firearm to defend against a knife. And he shot four times," defense attorney Mark Gardner told Susan Spencer.

Gardner knew from the start that a self-defense argument would be a tough sell.

"Many people's first reaction to it is, 'Oh, my God, you shot her four times, that's excessive,'" said Gardner.

"What did you have in your arsenal to counteract this?" Spencer asked.

"Physical evidence," Gardner replied.

Evidence, like the pattern of the shots Gonzales fired into Julie's chest.

"The tight grouping of the shots is consistent with his training, which is basically to fire until the threat is ended," Gardner explained.

"...she came at him suddenly and ... he put up his hand to push her away," he continued. "... suffered a superficial wound on his left forearm. She ... came back at him ... and he ... shot her."

But Prosecutor Kristin Bird was sure none of that ever happened. She says Gonzales staged the whole scene, from putting the knife in Julie's hand down to pretending to be sick when he called 911.

"The scene really didn't add up," Bird told Spencer. "There was no vomit anywhere ... and I would've sworn after listening to that call that he had been throwing up all over the kitchen."

Gonzales says he was only dry heaving. As to his claims of doing CPR, Bird says if he did it, he was amazingly neat about it considering that Julie had been shot four times.

Dash cam captures response to shooting at FBI... 01:11



"I would've expected more blood on the body. I would've expected blood on his hands. I would've expected blood on his clothes. We watched the cruiser video. We watched him come out of the house. He looked pristine," Bird told Spencer. "He did not look like a man who had been doing CPR for 10 minutes on his wife."

And then there is the question of the gun itself and where it was when Gonzales had lunch that day with -- as he first put it to detectives - a "friend."

"He and Cara have lunch," Olsen said. "His whole life was Cara Kast."

Security camera video shows Gonzales with his girlfriend, and he was not wearing his holster.

"If he didn't have the gun on his hip, he didn't draw it from the holster ... and shoot Julie Gonzales in response to some deadly threat," prosecutor Eric Olsen told Spencer.

"At what point does he put on his gun?" Spencer asked.

"I think he put on his gun after he shot her," he replied.

"He says he put his gun on when he got back from lunch and before he got into his car," said Gardner.

Asked why, he told Spencer, "Because he was trained -- to wear his gun -- normally."

"Why didn't he wear it to lunch?" Spencer asked.

"He had taken it off ... not intending to go to lunch. And then changed his mind and went to lunch and didn't put it on," said Gardner.

At trial, Art Gonzales testified that just before Julie came at him, she asked him a strange question: "Does Cara know the boys?"

"Art says 'Yes,'" said Gardner.

"And that's the catalyst?" Spencer asked.

"I can't crawl inside her mind and say that I know that's what provoked her to lose control and attack him," Gardner replied. "But, the sequence of events is that they had that very brief conversation, and then she attacked him with a knife and he shot her.

After eight days of testimony, the jury struggled through almost 26 hours of deliberation.

"It was ... one of the longest jury deliberations that I've been a part of. You just agonize over it," said Gardner.

"I've never seen a jury work harder," Bird said. "But at the end of the day, we -- we had a hung jury."

A very lopsided hung jury: 10 votes to acquit and only two to convict.

"I think that witnesses who testified about use of force ... were pretty compelling," said Gardner.

But the state would not let go. Ten months later, the Commonwealth of Virginia tried Art Gonzales a second time with a new jury, but the same judge. Both sides presented similar arguments. Gonzales testified again about Julie's drinking, her irresponsible behavior, and said again, when she came at him with that knife, he had no choice.

"We're ... not saying that she's an evil person," Gardner told Spencer. "But we're saying that she's human. She lost control of herself, for whatever reason. ...We are saying that."

At the second trial, juror Mary McDonald questions whether Gonzales was really wounded defending himself.

Scratches on Art Gonzales' arm

"The scratches on his arms definitely weren't very deep," she said.

As for the torrid affair with Cara Kast, Kast did not testify at Gonzales' trial.

"I sat there and thought to myself that, 'Wow. Why would you do that? Why would you be so open -- especially when you're going through a divorce?' I felt that he ... wasn't thinking clearly with his brain. It was definitely the wrong thing to do at the wrong time," said McDonald.

McDonald was inclined to believe Julie Gonzales had drinking problems, but she knew there was no alcohol in Julie's system the day she died.

"She was trying to get her life back," she said. "She was actually trying to do what was right for herself, and get better."

Fellow juror Paul Brastrom wondered who better to cover up a crime than a FBI agent.

"If there was anybody that could try and pull something like this off, he's a guy that would have all the answers," Brastrom said. "This is what he does for a living."

"So if anybody would know how to stage -- a crime scene, you thought it would be a well-trained FBI agent?" Spencer asked.

"Absolutely," Brastrom replied. "Right, that was in our thought process."

But, unlike the first jury, this one heard some startling new evidence from an expert who testified that one of the bullets that hit Julie was stopped by a hard, flat surface -- meaning she was on the floor when it was fired.

"She wasn't up against a wall," Olsen said. "The only possible explanation ... is she was on the floor when that shot was delivered to her."

"What you're describing, then, is more like an execution," Spencer commented.

"I'm saying that she was shot on the floor," said Olsen.

To say that undermined Gonzales' story is an understatement.

"That certainly created a completely different issue that we had to deal with," said Gardner.

"That was huge?" Spencer asked.

"Yes, it was huge," the defense attorney replied.

It is also a huge leap in logic, says Gardner, who produced his own expert to testify that that bullet could have been stopped by something as simple as Julie's bra.

"We know that there was an altercation there, and we have a knife in Julie's hand, but with four gunshots in her," said juror Brastrom.

The challenge for the second jury is the same as the first: determine both the how of Julie Gonzales' death and the why.

"We're starting to see this -- darker side of -- of this otherwise--stunning ... special agent," said Brastrom.

THE TRIALS OF ART GONZALES

Faced with the mountain of confusing and contradictory evidence in the second Gonzales murder trial, the jury again struggles to figure out what it all means.

"I couldn't come to a conclusion as to whether ... she was on the floor or not," said juror Mary McDonald.

After just one day, worried prosecutors make a major concession -- withdrawing the murder charge, giving the jury the option of voting for manslaughter.

"We were hoping that they were stuck between murder and manslaughter, and that if we took murder off the table it would signal to those dug in for murder that we just wanted the conviction at this point," Bird told Spencer.

It doesn't work. The jurors stay stuck and that afternoon, announces that they, too, are deadlocked. The vote was again 10 to two, but this time, it was 10 to convict.

"I felt he was guilty," Brastrom said. "...only two to acquit."

"I just didn't feel like they could prove that she didn't attack him," said McDonald.

A seemingly triumphant Art Gonzales heads home carrying his youngest son on his shoulders, perhaps underestimating prosecutor Eric Olsen's determination.

"We felt that ... the truth was coming out," Olsen said. "And that ... in a third trial ... we could get a verdict."

There would be a third trial with no chance of a hung jury, because this time, there is no jury. Both sides agree to a bench trial -- with some camera access -- with Judge Sarah Deneke, who has already heard this case twice, deciding Art Gonzales' fate.

"So now we have a situation where the judge is literally the judge and jury," Spencer noted to Olsen.

"Correct," he replied.

Meanwhile, Art Gonzales is free on bond, living with his sons in the very the house where he shot his estranged wife. Even with the reduced charge of manslaughter, he still could get 10 years behind bars. And that, says his friend Doug Merel, is a scary prospect for a loving dad and his sons.

"How do you think he's holding up?" Spencer asked Merel. "How is he feeling?"

"It's amazing to me that he's even holding up at all," he replied.

At his third trial, defense attorney Mark Gardner uses Gonzales' FBI training to defend what happened. His witnesses say the reflex to react ingrained in FBI agents is what keeps them alive.

Mark Gardner: What about the fact that Art fired four shots? Brian Kensel | Retired FBI Agent: Four shots with a handgun against an advancing attacker is very often insufficient to stop that attack.

Julie's parents, who have traveled across the country from New Mexico three times for these trials, aren't buying it.

"He's not takin' accountability for what he does," Rey Serna said. "What he wants you to believe is Julie is responsible for her own death."

"It was very difficult to look at Art when I got on the stand," said FBI agent Janet Johnson.

Art and Julie Gonzales

Johnson, who worked with Gonzales in New Mexico, says Art confided something to her before he moved to Virginia.

"'If I divorce her in New Mexico, she gets 50 percent of everything I have,'" Johnson said. "He goes, 'That's not gonna happen. I'm gonna lure her to Virginia ... And the laws are much more favorable to the man in Virginia.'"

Gonzales' attorney, Mark Gardner, says the physical evidence of what happened that day is the only evidence that counts -- evidence like the gunshot residue.

"There was gunshot residue, both on Art's hands and on Julie's hands. There was gunshot residue on the knife," he told Spencer. "All of that's consistent with his claim that she attacked him, was in close proximity to him when the weapon was fired."

Prosecutors agree the physical evidence is the key, and are hoping the judge will grasp it better than the two hung juries apparently did. They bring back their star witness.

Dr. Marcella Fierro is the renowned forensic pathologist who says Julie was flat on the floor when at least one of the shots was fired. What makes her so sure?

"This bullet then exited the back partially ... it exited and then popped back in because it has a shored exit," she testified. "It means that the back was against something firm or hard."

And that something, prosecutors say, was the kitchen floor.

But as in the previous two trials, the defense maintains the bra Julie was wearing could have stopped the bullet. Nonsense says Fierro.

"Could a bra cause shoring? The answer to that is, yes, but not the bra on this lady," Dr. Fierro told the court.

She is unshakable under cross examination. When asked by Mark Gardner what would change her mind, she replied, "A video."

But defense forensic pathologist Donald Jason is just as sure.

"I believe it happens with bras like she was wearing," he testified.

Even more surprising is a witness who typically testifies for the prosecution -- Dr. Jennifer Bowers, the state pathologist:

Mark Gardner: Do you believe the bra that you saw on Julie when she was brought to the Medical examiner's office -- could have caused that shoring? Dr. Bowers: It's possible, yes, sir.

In his closing arguments, defense attorney Gardner underscores the dilemma of dueling experts:

"I will go to my grave questioning how any forensic pathologist can say a .40-caliber bullet shot into Julie's body exited her back with enough force to hit the floor and cause shoring of that wound -- and there's no evidence that the bullet struck the floor," Gardner addressed the court.

"Julie charged at him, according to him -- surprised him. He looked up, he put his arm up and he pushed her away. He tried to create distance. She got her balance and immediately came right back at him. He pulled his weapon and he fired exactly like he's been trained to do.

"I maintain that there is no real evidence to contradict Art's claim about what happened in that kitchen," he continued.

But prosecutor Olsen says nothing Art Gonzales says can be trusted:

"It is not a coincidence that the track of Mr. Gonzales' relationship with Cara Cast is the track of the divorce," Olsen said in his closing arguments. "It was May, right at the beginning of May, is when he fell in love with Cara Cast, despite all his protestations to the contrary. ...What happens mid-May, after he's fallen in love with Cara Cast? ...he goes to see a divorce lawyer. What happens in June of that year? He files for a divorce.

"Mr. Gonzalez has lied repeatedly in this courtroom," Olsen continued. "He's lied about when the romantic relationship started and when the sexual relationship started.

"He is manipulative," Olsen said. "He is devious."

Two years after this once-respected FBI agent shot his wife to death, he is about to learn his fate.

DECISION FROM THE BENCH

"The only thing that I'm 100 percent sure of ... is that Julie Gonzales should not be dead," said Judge Sarah Deneke.

The prosecution had flown in Julie Gonzales' New Mexico friends to testify. After two hung juries and three trials, they are confident that, this time, justice will be served.

"And Lea and I just grasped each other," Kim Scott said. "And we thought, 'Oh My God. It's finally done.'"

"There is no rational or reasonable explanation for what happened in that house on August 19th," the judge continued.

But Judge Deneke seems in no hurry to deliver her decision.

"It was excruciating. I'd be lying if I didn't say that," said Gardner.

For openers, the judge clearly doesn't believe Art Gonzales' story about trying to resuscitate Julie after he shot her.

"The defendant reported performing CPR on the victim on Julie, and, um ... I find that very doubtful given the evidence that I've heard here," said Judge Deneke.

But then, she pivots, and begins dismantling the prosecution's case -- point by point:

"We have to address the issue of Cara Cast," the judge said. "The court finds that the evidence of the relationship with this girlfriend is irrelevant to this finding. ...there was not one single piece of evidence that is relevant to motive or motivation...

"...his girlfriend ... what he considered the love of his life, he found out that she was goin' with someone else ... that couldn't have played a part ... in his mind when ... when he killed Juliandra," Rey Serna said of the judge's finding. "To her, it didn't matter."

"Now the evidence is ... that the bullet was somehow caught in the clothing," Judge Deneke continued. "Frankly ... I find that weird ... it's not significant in terms of making a determination as to whether or not this, um, crime occurred, or this killing occurred in self-defense."

"This is not relevant ... That's not relevant. ...She went through a whole list of that she found was irrelevant," Serna said. "All of the things that happened to him that made him unstable ... distraught ... she said that didn't matter."

Nor do the dueling expert witnesses sway the judge.

"They do not vary on the facts," Judge Deneke said. "They all agree that there were four shots."

What apparently does matter to the judge is the gunshot residue on Julie Gonzales' hands, which leads her to conclude that Julie indeed may have attacked Art Gonzales.

"The gunpowder residue is consistent with the defendant's version of the victim holding a knife as he fired the weapon," Judge Deneke said. "There's no other explanation as to how she could have gunpowder residue on her hands."

Accepting that Gonzales' story could be true, she announces her verdict -- sounding almost reluctant.

"I have no choice ... but to find the defendant not guilty of the crime of manslaughter," Judge Deneke ruled.

"When she says ... those final words are ... not guilty ...my heart sinks," Prosecutor Kristen Bird said. "You know, you're just totally devastated."

"It was disbelief...shock," Rey Serna said. "It was a miscarriage of justice."

The verdict is more than Prosecutor Kristin Bird can take.

"You were sobbing," Spencer noted to Bird.

"I had heard the family gasp behind me at the end of the reading of the verdict," she explained. "And it was hard to know, that for a split second there at the end, they thought he was gonna be found guilty."

Despite the outcome, Prosecutor Olsen defends trying Gonzales three times.

"We believed strongly that he was culpable and guilty of the death of Julie Gonzales," Olsen told reporters outside the courthouse. "We wouldn't have prosecuted the case if we had any doubt."

A free man at last, Gonzales quickly exits the courthouse, his family shielding him from view. His sister, Arlene, stood by him throughout the entire ordeal.

"It's a relief and our family is very happy...I'm sorry," she told "48 Hours," overcome with emotion.

Gonzales showed up uninvited when "48 Hours" talked with his lawyer. He didn't want to join the interview, but he kept his ear to the door for the entire time.

Art Gonzales listening at the door during Susan Spencer's interview with his lawyer Charlotte Fuller/CBS News

In the end, standing in the doorway, Gonzales would only talk about his reaction to the verdict:

Art Gonzales: I'm sorry, do you mind if I, for a second Miss Spencer, what... I'm kind of hearing through the door and stuff, but what did the prosecutor allege I did right after the verdict was read? Susan Spencer: Nothing, I didn't ... nothing. Art Gonzales: Oh... Susan Spencer: No, I asked, I said I couldn't see. I said I was sitting behind you, and I couldn't see. And I asked what your reaction was. Art Gonzales: I looked up and I thanked God. Without God and the people he's put in my life, there's no way I could've made it. Susan Spencer: You can come say that to me. Art Gonzales: I will -- in time. Susan Spencer: Well how about now? Art Gonzales: No, because I have to take my son to soccer practice.

Art Gonzales never did sit down with "48 Hours." Now a single parent, he's says he's stretched thin -- plus the FBI fired him for what it said was his "lack of candor" during the murder investigation.

"His life has been in limbo since this happened," Gardner told reporters. "He's been without work, he's been unemployable ... essentially lost all of his assets ... his house is up for sale."

But you'll find little sympathy for Art Gonzales in Julie's hometown of Socorro, New Mexico.

"Not in my worst nightmare did I ever ... think that ... we would be goin' through something like this," Rey Serna said.

Julie Gonzales with her father, Rey Serna Serna family

Her parents can only take comfort in their faith and their memories.

"What will you miss most about her?" Spencer asked.

"Her gentleness, her good nature ... her wittiness," said Serna.

Once very close to their grandsons, Rey Serna says they hardly get to see them now.

"We lived for our grandchildren ... I was their teddy bear...what more can I say?" he said. "We love them, and we'll always love them."

Through three trials, they believed in their hearts that the FBI agent who killed their daughter would go to prison for it. Now, they believe something else entirely.

"Art Gonzales is guilty of murder ... And he got away with it," Ret Serna said. "I'll believe that till the day I die."

Cara Kast married the other FBI agent she was involved with.

The couple now have a child.