Produced by Patti Aronofsky, Elena DiFiore and Lourdes Aguiar

"I'm in the Hudson River, my fiancé fell in the water, can you please call anybody. ... I can't get to him. It's very windy and the waves are coming in and I can't paddle to him. He is getting further and further away from me ...he's gonna drown!"

It was the evening of Sunday, April 19, when Angelika Graswald made a desperate sounding call to 911.

"At approximately 7:30 in the evening I got a phone call ... that there was a situation ... a capsizing of a kayak," said Jeff Schaack, commodore at the Cornwall Yacht Club in New York's Hudson Valley.

Graswald's call was obtained by "48 Hours":

Angelika Graswald: He's gonna drown. Please call somebody-- 911 operator: We've got help on the way. Angelika Graswald: The waves are very strong. I can see his -- I can still see his head... 911 operator: OK. Angelika Graswald: Hold on, baby!

"It did get choppy out. Three to four-foot swells. ...I would never be out there," Schaack told "48 Hours" of the conditions on the river."They immediately went into the work boat ... to help rescue this person."

Angelika Graswald: I can't see him anymore. 911 operator: You don't see him? Angelika Graswald: No.

The sun was setting; the river turning dark.

"They pulled her out of the water," Schaack said. "They never saw another person in the water."

Vincent Viafore's body had been swallowed up by the river. It all appeared to be a tragic accident. But within days, investigators heard disturbing reports that Graswald seemed oddly unaffected by his death. She agreed to be questioned. In the dramatic police interrogation video, Graswald's own words turned her from a grieving fiancée into a murder suspect.

Joel Goss has known Graswald for almost seven years. He saw Angelika toiling in local restaurants, but knew she had bigger dreams.

"She was always very nice ... bright and clever and perky," Goss said. "Photography. She - she really wanted to do photography. ... absolutely blissful when she was doing that."

Sheri Parte tended the bar.

"She would always take pictures of the sky, or something. You know, flowers. She always found beauty in that," Parte said. "I thought that she had a good heart, you know. I don't have friends who don't have good hearts. You know?"

Vincent Viafore and Angelika Graswald

She was born Angelika Lipska in Latvia, when it was still part of the Soviet Union. When the Iron Curtain lifted, she sought opportunity -- a nanny job bringing her to the United States. And by the time she met Vincent Viafore, Angelika had been married and divorced twice. But then, so had he.

"It was love at first site," Parte told "48 Hours" correspondent Peter Van Sant.

Nearly 11 years older than Graswald, Vincent Viafore, 46, was a project manager with the State of New York, and one of Parte's closest friends.

"What was it about her personality that he fell in love with?" Van Sant asked.

"She was spunky like him," Parte replied. "They just knew that they wanted to be together."

Amanda Hoysradt was Viafore's roommate at the time

"He loved her. He wanted to be around her all the time," she said.

Within weeks, Graswald moved in.

"Did he wanna marry Angelika?" Van Sant asked.

"Yeah, he was even talkin' about having kids," Parte replied. "And, he hadn't done that before."

Known for his BBQ ribs, his dance moves, and his partying, Viafore was as generous and fun as they come.

"Vinny had a lot of friends?" Van Sant asked.

"A lot of friends," Hoysradt replied. "...like, 'The party's here! Let's take a shot. You guys want a shot?' His other little nickname is Vinny Shots."

Like in a photo taken on Saturday night, April 18, when Viafore was out to party with his friends. It was just 24 hours before he would go kayaking.

"Vinny wanted to stay out havin' drinks with us, because that was, like, we hadn't gotten together in a couple weeks," said Hoysradt.

Maybe even go to a strip club. But Graswald wasn't interested.

"She wanted to go home, Hoysradt explained. "She was quiet. You know, she wasn't really talkin' to anyone."

Before Viafore took her home, he told Sheri Parte's boyfriend, Monte Nesheiwat, he had wanted to go kayaking.

"I was like, 'What are you crazy? Look behind you.' ...The water was choppy. It was really cold ... 'you can't go in the water. Don't even think about it,'" he said. "You can't talk Vinny out of anything he's ... he's very, you know ... he loves adventure."

Graswald herself would take police through the very same Saturday night in an interrogation - the video obtained by "48 Hours":

Investigator: Did you guys get intoxicated? Did he get intoxicated? Angelika Graswald: That Sat --Saturday night? Investigator: Yeah. Angelika Graswald: Yeah, he did.

Graswald tells the investigator things between her and Viafore were tense - they argued, but then made up:

Investigator: How did the fight end? Angelika Graswald: By us going to bed and snuggling.

The next day, Sunday, April 19, Viafore was determined, she says, to go kayaking.

"'We're going, we're going,'" she told police.

Year after year, kayaking in the Hudson was something of a spring ritual for the couple. The days were warming, but the river still cold. That day, Graswald says Viafore packed their gear. Traffic cameras caught his vehicle heading out.

"I had my life vest, I had my purse," Graswald told an investigator.

But she says Viafore didn't take a life vest for himself. Their plan this trip was to head to Bannerman's Castle, located on an island in the middle of the Hudson River, where Angelika would change into something sexy for photos.

"Well, I wanted to please him," she told an investigator.

Just after 4 p.m., they launched. Bringing alcohol -- beer can be seen in an evidence photo -- and when they arrived they headed up stairs that led to the castle. Because it was very cold and windy, Graswald says they decided to start the journey home around 7 p.m. At first, she says Viafore was enjoying the rough water and was playing around.

"He pulled forward in front of me and said, 'Baby, this is an adventure of a lifetime,'" she told an investigator.

Graswald tells police she knew Viafore's kayak was missing its drain plug, which is supposed to cover a hole in his kayak. And she says while his kayak worked fine without it on the way out to the island in a calmer river, now with the waves, she was concerned about him.

"The waves are doing their thing, up and down like that," she motioned with her arms. "I saw that it started to fill up, and I knew that the plug wasn't there."

Then Viafore was suddenly in the water, holding his seat cushion that floats, Graswald says, his kayak and a dry bag. Angelika took his paddle and hooked it to her kayak.

"He's in the water, I have both paddles ... and the waves are pulling me away from him further and further. And that's when he yells, 'Call 911!'" she continued.

In the minutes and hours following that 911 call, Graswald's every action would be closely scrutinized.

It was Monday morning when Sheri Parte heard the news.

"I called Angelika. She picks up. I said, 'I'm freaking out," she told Van Sant. "I'm like, 'Angelika, what's going on? Like, is there something wrong?" She's like, 'Vinny is missing.'"

But Graswald, she says, was bizarrely calm. While divers searched for Viafore's body, Angelika posted video of herself doing cartwheels on her Facebook page.

"I thought it was a little insensitive," Parte said.

Graswald also posted an old picture of herself kayaking in bad weather.

"[It's] kind of creepy that she's there alone," Parte commented, "and it's a stormy day. It was kind of freaky."

But Joel Goss didn't see Graswald in the same light.

"I believe she was absolutely in pain that Vincent was gone," he said.

Goss says Graswald was really trying to put on a happy, brave face.

"So she was hopeful, saying, 'There's still a chance they'll find him. There's still a chance,'" he explained. "'I should put flowers where I last saw him. I should put flowers there.'"

So 10 days after her fiancé went missing, Graswald went back with flowers in hand to Bannerman's Island. Police were there, too; not to comfort Angelika, but to confront her.

QUESTIONING ANGELIKA

For days on end, the scenic river where Vincent Viafore loved to fish and kayak teemed with rescue boats and helicopters looking for his body.

"I prayed every day ... to help us find him ... whether he was alive or not, to -- to bring him home," his mother, Mary Ann Viafore, said."You woke up anxious, you know. Hopefully, is this the day you're gonna find him?"

While search crews combed the waters, Viafore's loved ones got news that left them reeling.

Stunningly, police now believed Viafore was murdered on the river and that his fiancée, Angelika Graswald, killed him. Investigators say that when they questioned Graswald on Bannerman's Island, she gave them some extremely incriminating answers.

"She made statements that implicated herself in - in this crime," Major Patrick Regan of the New York State Police told reporters at a news conference.

The drain plug that was removed from Viafore's kayak

Authorities say Graswald admitted she removed the drain plug from Viafore's kayak.

Investigators believe that caused the boat to fill up with water. They also believe that she tampered with his paddle --removing a ring, which helps keep the paddle securely together. And then, when Viafore went into the water, they say that Graswald took the paddle away from him so he couldn't use it as a floatation device.

"It was a -- a complete shock," Mary Ann Viafore said. "And I was devastated that -- that-- she would do that to my son, who was so good to her."

Angelika Graswald

Angelika Graswald, 35, was charged with second-degree murder, and later, manslaughter.

"If somebody told me this was in her future, I wouldn't have believed it for a second," said Michael Colvin, who lived with Graswald in 2009.

Colvin cannot imagine that his ex-girlfriend is a killer, but he does remember she had a dark side.

"Did Angelika have a temper?" Van Sant asked.

"Absolutely," Colvin replied. "...she certainly had an anger streak."

Colvin witnessed that anger in his driveway shortly after they broke up. It involved Mietka, the cat they had adopted together.

"She insisted on getting the cat and threatened to break into the house if I didn't give it to her," he explained. "The car's running ... I'm getting into the car ... she laid down just like this in the driveway, flat like this," he demonstrated, laying on his back. "'Give me the cat. ... Give me the cat,' to which, of course, I -- you know, finally at this point, she's laying down in my driveway, I'm not gonna run her over, so I gave the cat to her."

"The woman definitely has a way of reacting when she feels threatened, there's no question about that," Colvin continued.

"To lay behind the car, to threaten to break in, and you don't even have a place to house this cat ... that's the extreme side I think," Colvin's wife, Heather added.

Vincent Viafore's friend, Sheri Parte, says Graswald could violently turn on him when she was drunk.

"She would smack him so hard across his face and -- and he would just look at her and be like ... he would not get mad. And she'd do it again and she'd do it again," she explained.

Just two weeks before his kayak capsized, Amanda Hoysradt says Viafore texted her, expressing some doubts about his relationship with Graswald.

"You know, he didn't think it was gonna work," she said.

But the very next day, Hoysradt says, he changed his mind.

"'He's like, 'Oh, well, she must be really afraid of losing me, because she wants me to stay home and we're gonna make up,'" she said.

"Do you think he ever expressed that to Angelika ... that maybe we're having some problems here. Maybe we shouldn't do this," Van Sant asked.

"Yeah," said Hoysradt.

"I think so," Parte agreed.

In fact, in the 11-hour interrogation, Graswald told police they were having problems. She said Viafore was pressuring her for things she wasn't comfortable with.

Angelika Graswald: ... he pushed for everything. He pushed for -- for sex, for sexual stuff. Investigator: OK, he always wanted sex ... Angelika Graswald: Yeah. Investigator: ...and you to do sexual things? Angelika Graswald: Well, yeah. Investigator: OK. Angelika Graswald: He wanted threesomes, porn, everything. Investigator: OK.

Graswald said they fought about it:

Investigator: And how does it make you feel Angelika Graswald: Angry. I was angry. Investigator: Very angry? Angelika Graswald: Yeah.

And Graswald admitted that she often felt trapped in the relationship, sometimes wishing Viafore was dead:

Investigator 2: Why did you want him to die? How could you best put it? Angelika Graswald: I wanted to be free.

"I wanted to be free." As startling as that admission was, Angelika made even more disturbing comments to investigators:

Investigator 2: And you feel happy -- Angelika Graswald: Yes. Investigator2: --- and relieved that it happened? That he's dead? Angelika Graswald: Yes. Investigator: When you watched him in the water, was a part of you sayin', "My worries are goin' away now, and I'm free." Angelika Graswald: Yeah. Investigator: And were you almost-- Angelika Graswald: Euphoric. Investigator: Euphoric that he was-- Angelika Graswald: Yes. Investigator: --gonna be gone. Angelika Graswald: I just -- I was ... [unintelligible] Investigator: You felt that way? Angelika Graswald: Yes. I still do.

Along with anger, prosecutors say Graswald's other motive for murder was money. She stood to gain $250,000 from two of Viafore's life insurance policies -- a financial windfall for someone who had no money of her own.

Angelika Graswald Times Herald-Record

Angelika Graswald pleaded not guilty and was now on her way to jail to await trial. Her bond: $9 million. Prosecutors considered the Latvian native a serious flight risk and a judge agreed.

"It's like how -- how dare you feel that you can play God to decide when somebody's time is up," Sheri Parte said in tears.

But defense expert Michael Archer says Graswald's alleged confession during that lengthy interrogation is meaningless. He says the forensic evidence tells the true story.

"I haven't seen all of the evidence, but the evidence I've seen certainly does not support ... a homicide," he said. "This is, by all accounts, a tragic accident."

And, Archer says, he can prove what really caused Vincent Viafore's kayak to capsize.

"The police theory of this case is really outrageous," Archer told Van Sant.

TESTING THEORIES

"The water is somewhere around 46 degrees at the warmest. You know this is very cold water. It's frigid water. It's getting dark. It's windy. The waves are three to five feet high. He has no life vest on. And he has some level of impairment by alcohol. All of those fit that this is an accidental death," said Archer, a forensic scientist.

Archer grew up in the Hudson Valley and knows this beautiful river can be treacherous.

"I'm not gonna blame Mr. Viafore," he continued. "But he certainly wasn't as cautious as he should have been."

Working for the defense, Archer has spent months examining the prosecutor's evidence against Angelika Graswald.

He asked Buddy Behney, of Mountain Tops Outfitters, to paddle out on the Hudson River in the same model kayak as Vincent Viafore did. Behney is an experienced kayaker.

"Buddy, how much do you weigh?" Archer asked.

"About 180, 185," Behney replied.

"So Peter, here's a gentleman who's significantly smaller that Mr. Viafore and I just want you to see how low that kayak is in the water. And I'm not gonna say this water's like glass, but it's pretty calm today," Archer pointed out.

"If you were in rougher water, would you be struggling to remain upright?" Van Sant asked Behney.

"Absolutely. Yeah. ...just the wake from that boat had me a little tipsy, a little nervous at one point," he replied from the kayak. "It's definitely more designed for, you know, small ponds, lakes, thing that. You know, water that's generally calm all the time."

Behney paddled from Bannerman's Island to the area where Viafore and Graswald launched, about a mile away, with the drain plug open. Remember, Angelika is accused of removing the plug from Vincent's kayak.

"Do you feel the boat filling with water because the plug is out?" Archer asked.

"If there's any water getting in there at all it's very minimal. I don't feel it. I don't notice it. I don't see anything," Behney replied as he paddled.

That may sound surprising until you take a closer look.

"This is the kayak ... this photo was taken by the New York State Police," Archer said, referencing a photo on a computer monitor.

"This is the kayak that Vinny was in?" Van Sant asked.

"Yes, that was the one Mr. Viafore was in. So, he's sitting here," Archer said of the cockpit. "The plug is on top of the boat, and the point of the plug is..."

"Wait a minute. The plug is on the top of the boat?" Van Sant asked.

"The plug is on top of boat," Archer affirmed.

"Well, how can it fill up with water if the plug is on top?"

"It doesn't," said Archer. He described the plug as being "about the size of my pinky."

"It's funny, I believed also that the drain plug was at the bottom of the kayak," said Jeff Chartier, one of Angelika's defense attorneys.

Vincent Viafore's Fusion 124 model kayak

Chartier says the Fusion 124 model kayak was designed with the plug on top so, once back on land, it can be easily flipped and drained.

"Where do you believe the water actually came into this boat?" Van Sant asked.

"Well, I think it's pretty clear. Look at the size the ... big giant hole," Chartier said of the kayak's cockpit.

"And this is what led to the tragedy?" Van Sant asked.

"Absolutely," Archer replied.

"No doubt," added Chartier.

That's the defense theory. And while Archer can't recreate the exact conditions the day of Viafore's drowning, he did design an experiment to prove the defense's point -- strapping the kayak to the back of a boat and then creating an artificial wave - with the plug out and the cockpit area wide open.

"We're gonna restore this kayak to the way Vince used it that day on April 19," Archer explained. "And we're gonna see how much of that wake ... comes in and how much water gets in the cockpit area, how much water gets into the plug area."

"Got the plug. Fire it up skipper. Let's go," said Van Sant.

"Peter, come look at how our wake fills this boat," Archer said.

"Wow. And that was about a three-footer coming into this," Van Sant remarked from the boat.

"Absolutely."

"That's just one wave coming in. Take a look at this. This looks to me a quarter full with just one wave," Van Sant observed.

Archer then devised a test to see how much water could actually enter the kayak through that tiny hole.

"So Peter, what I wanna do is I'm gonna dry the boat out," he explained. "We put a cockpit seal over top. We've sealed up the cockpit area. We've taped it up so it's on there good. It's tight. And we've left the plug open. And we're gonna ... have the water come over the kayak and see just how much water goes into the plug."

"What do you see," Van Sant asked.

"There's not that much Peter ... let's get that five-gallon bucket, see if we can fill it up," Archer said, then asked for an empty water bottle.

Peter Van Sant, with Michael Archer, holds a bottle with the amount of water drained from the kayak's drain plug opening

"This bottle is 16.9 ounces," Archer remarked of what the empty bottle could hold.

"That's less than an ounce," Van Sant remarked to Archer after draining the water from the plug.

"What does that tell you?"

"That for what wouldn't fill a shot glass, a woman is sitting in jail being charged with a murder," said Archer.

But Angelika Graswald is also accused of tampering with Viafore's paddle -- removing the ring that police believe holds the two sides of the paddle together.

Archer asked Behney to paddle the journey with the ring removed.

Asked how the paddle was holding up, Behney told Van Sant, "No problem."

"You don't need the ring to use the paddle," said Archer.

The other damning allegation against Graswald is that she took the paddle from Viafore after he went into the river, denying him something to hang on to. But could it have saved his life?

"I've taped a four-pound brick to the paddle and we're gonna see whether it sinks or floats. If it sinks with a four-pound brick attached, it's certainly not gonna support a full-grown man," Archer said standing in the river, the paddle sinking quickly. "And there you have it, another one of their theories that just doesn't hold water."

But what this forensic expert can't explain is what Graswald said to police. But "48 Hours" spoke with an interrogation expert who believes he can.

A FALSE CONFESSION?

Jim Trainum knows a lot about interrogation rooms.

"This is your typical police-style interrogation room. Four walls, no windows, and a door ... very sparse, very bare. No clocks ... nothing to distract you," he told Peter Van Sant.

"We wanna get you into our environment so that we have control over the situation," Trainum explained.

For 27 years, the former detective for the DC Metropolitan Police Department conducted hundreds of interviews and interrogations. But there's one interrogation that still haunts him - when he unwittingly got an innocent woman to confess to murder. She later sued him and the police department.

"We get the person to believe, at least temporarily ... that it is in their best interest to tell us what we want to hear. ...Anybody can fall victim to it," Trainum said. "And every single person can potentially give a false confession."

Trainum is now considered a national expert on false confessions -- teaching, writing, and testifying in high-profile cases. "48 Hours" asked him to review the case against Angelika Graswald.

"You haven't been hired by the defense team?" Van Sant asked.

"No, not at all," Trainum replied.

"And you come in with no bias?" Van Sant asked.

"I -- have no dog in this fight," said Trainum.

He watched every moment of Graswald's 11-hour interrogation.

"Would you use this to teach other cops how to do a proper interrogation of a suspect?" Van Sant asked.

"I would use it to teach them how not to," said Trainum.

Trainum's investigation began with a document obtained by "48 Hours" -- a record of what Graswald allegedly told investigators on Bannerman's Island.

"You've read this document - any red flags there?" Van Sant asked.

"A lot of red flags," Trainum replied.

According to the document, Graswald essentially admits tampering with Viafore's paddle and the drain plug to kill him. "What did you do to make him drown?" -- they ask. "I took the plug out of his kayak," she answers.

"Precise, perfect questions. Precise, incriminating answers from Angelika?" Van Sant asked Trainum.

"Right," he said.

And you would expect the video interrogation of Graswald to mirror that -- but it doesn't.

"If you compare the statement, it doesn't match the video at all," said Trainum.

Police took Graswald from the island and read her Miranda rights -the right to remain silent and have a lawyer.

They tried over and over to get her to repeat on camera what she supposedly told them on the island:

Investigator: What could you have done physically that caused him to drown? And let's see if you remember what you told me. Angelika Graswald: No... Investigator: You said by taking the plug out of the kayak and taking the ... paddle away from him. Does that sound correct? Angelika Graswald: Yeah, but I didn't intend to have it happen that way.

"There's definitely clear signs of manipulation here, where they want a specific answer from her," said Trainum.

The investigator tries a gentle approach:

Investigator: It's therapy for you. Angelika Graswald: Of course. Investigator: And like I said, you'll feel better.

"The way they approached her," Trainum noted. "'This is therapy. We're just trying to get to the bottom of this. This is going to help you.'"

Graswald reveals intimate details of her life - claiming Viafore demands that she participate in a threesome. Demands that made her angry:

Investigator: By the way he treated you, you taking that plug out was a reaction of - of -- Angelika Graswald: The way he treated me... Investigator: The way he treated you, right?

"They've been trying to establish motive the entire time," Trainum explained. "They're asking numerous leading questions. ...they're telling her the direction that they want they answer to go. They're often giving her the answer."

Investigator: Like that was almost a way to get back at him? Angelika Graswald: Kind of ... yeah.

"You see where they think they have her. That they have an admission. And then three or four, you know, questions down the road, she's going, 'No, I didn't want him dead,'" Trainum continued.

Investigator: You watched him drown. I know it's difficult. I know... Angelika Graswald: I didn't just watch him drown. I tried to do something about it.

A second investigator comes in, repeatedly trying to get her to own what he believes she did.

"Typically this is done because the first investigator is getting nowhere," Trainum said. "And, as you'll see, he's more of the bad cop and the first guy is more the good cop."

Investigator 2: When did you in your mind make your decision, Vinny needs to die and I'm going to take some steps to make sure that happens? Investigator: And be free. Investigator 2: And be free. And be out of this controlling possessive relationship? Angelika Graswald: I wasn't thinking that at all. Investigator: What did you want that day? Angelika Graswald: That day? I wanted to be free. Investigator 2: And you wanted him to die? Angelika Graswald: ...if you put it that way. Interrogator 2: I'm not putting it that way. Well, what's the answer? You know what the answer is. What's the answer, Angelika? Angelika Graswald: I wanted him gone. Investigator 2: And that would set you free. Angelika Graswald: I didn't want him, like, gone, gone.

"To them, that you know, that 'gone' part meant you wanted him dead. I think she means something totally different when she's saying it," Trainum said. "She's using the term 'gone' as out of the relationship."

Analyzing the interrogation video, Trainum believes the investigators had tunnel vision. He says their entire case is built on a false premise.

"They think they know the truth," he said.

That Graswald pulled a plug in Viafore's kayak and it caused it to flood with water. But Trainum says the investigators are clearly confused, believing the drain plug is on the bottom of the kayak -- when it's on the top.

Investigator: Where does that plug go on the kayak? Angelika Graswald: It goes all the way in the back, and it drains it. Investigator: Like, underneath it? Angelika Graswald: No. Investigator: No?

"He thinks it's on the bottom," Van Sant remarked to Trainum.

"Yes, in fact later on, he again brings it up," he replied.

Investigator: And, that's underneath it? Angelika Graswald: No. Investigator: No, it's on the top, right? Angelika Graswald: It's on the top.

"I think a good defense lawyer could have a field day with this," Trainum said. "If that plug being out did not cause that kayak to fill up with water, it doesn't mean a damn thing."

What's more, Graswald insists she removed the plug months before the April incident - in the winter -- when her kitten was playing with it.

"It doesn't help their case if she took out that plug so long ago," said Trainum.

If Graswald's telling the truth, Trainum asserts, it's hard to argue she planned to kill him.

Investigator 2 : When did you take it out on Sunday? Angelika Graswald: I did not take it out on Sunday. The plug was already out. Investigator 2: The reality is you took that plug out because you wanted to kill him. You wanted him to be dead. You wanted to be free? Angelika Graswald: I took it out before - Investigator 2: Yes. Angelika Graswald: A long time before. Investigator 2: Because you wanted him to die? Angelika Geaswald: Yes, at some point yes. Investigator 2: So in essence it's exactly what we're saying. We're, like, talking semantics.

"They've been twisting her responses," said Trainum.

But hours into the interrogation, Graswald finally sort of agrees with them: "I took the plug out," she told investigators. "April."

April -- the month the tragedy occurred. Trainum says don't trust that.

"Do you believe that every person has a breaking point in an interrogation?" Van Sant asked.

"Oh, absolutely," said Trainum.

Repeatedly throughout the long interrogation, Graswald says she needs to go care for her beloved cat.

"Why don't we wrap this up. And I need to see my cat," she said.

"She's worried about her cat," Trainum said."She's gonna agree to their narrative in order for her to get out of there."

And, he says, she does just that:

Investigator 2: By taking that plug out you killed Vinny. Correct? Angelika Graswald: Correct. Investigator 2: And you wanted that to happen, correct? Angelika Graswald: Correct. Investigator 2: And you feel happy? Angelika Graswald: Yes. Investigator 2: And relieved that it happened? That he's dead. Angelika Graswald: Yes.

Graswald has now been in the interrogation room almost six hours:

Investigator 2: You killed Vinny. Right? Angelika Graswald: You want me to... Investigator 2: No, I want you to tell me the truth. Angelika Graswald: I am telling you the truth. Investigator 2: And what is the answer to that question. Angelika Graswald: I didn't. I didn't. Investigator : No. Investigator 2: Angelika, what is the true answer to that question? Angelika Graswald: All right, I'll give you a f-----g statement! Investigator 2: What is it? Angelika Graswald: I wanted him dead and now he's gone. And I'm OK with it...

"I think she's done," Trainum noted. "She's now getting more and more desperate to get out of that room."

"I sense, the more you watch this, the more you're becoming convinced that this is a false confession?" Van Sant asked.

"Yes," Trainum replied. "To me this is a non-crime. This is an accident that they made into a criminal offense because of their gut feeling because of her not acting appropriately."

"48 Hours" wanted to question the prosecutor about the allegation that the State's case may be founded on a false confession. A spokesman said no comment will be made before trial.

"Should Angelika Graswald be in jail right now as we speak?" Van Sant asked Trainum.

"Absolutely not. Absolutely not," he replied.

REMEMBERING "VINNY"

Amanda Hoysradt and Sheri Parte and have been living a life of torment since the terrible day their friend, Vincent Viafore, went missing.

"The fact that it was so mysterious and nobody could figure it out. And we were wishful thinking and going on searches for him and looking for him. It was -- it was like we didn't have a sense of peace," Hoysradt told Peter Van Sant.

"We haven't had that closure that most people get when you lose somebody, you know? We haven't had that," said Parte.

And calling the state police for any news became a sad routine for Vincent's mom, Mary Ann.

"I talked to the state police a couple of times a week. It was hard," she said. "We were all praying."

Vincent Viafore Mary Ann Viafore

On Saturday morning, May 23, 2015, the agonizing wait came to an end.

"I was both sad and happy. Sad that -- there was no hope. And happy that at least we found him and could bring him home," said Mary Ann Viafore.

Vincent Viafore's body was found by a boater about a mile downstream from Bannerman's Island.

"I had an anxiety attack. I had a panic attack," Parte said. "...it was bittersweet."

Angelika Graswald's defense team is hopeful that once an autopsy is performed, the murder charge against her will be dropped.

"The state police desperately need this to be a homicide to support their murder charge," forensic scientist Michael Archer told Van Sant. "And I don't expect her to rule this a homicide, 'cause there's no evidence to support that this is a homicide."

But just weeks later, the medical examiner's report confirmed that Viafore died by drowning and that he had a blood alcohol level of .06, which is considered being impaired.

Yet the manner of death was ruled a homicide -- the medical examiner noting that the drain plug had been intentionally removed.

Graswald's lead defense attorney, Richard Portale, insists that Angelika is not to blame here.

"Mr. Viafore was responsible for that kayak. And, you know, the -- you're the captain of your own ship. And he left Plum Point on -- on April 19th, and he had no life vest," Portale said during an interview on"CBS This Morning". "He knew the temperature that water was. And so he was responsible for his conduct on that day."

Viafore's friends are not really sure what to think.

"Could this be a tragic mistake? A tragic accident?" Van Sant asked Vincent's friends.

"Anything is possible. I mean, I don't have enough information to even make that decision. That's what's so frustrating," said Parte.

"I don't know the right or wrong answer," Hoysradt replied. "Everything is looking like she did do it. It's where I'm torn. I don't know."

Vincent's mother, however, is less conflicted.

"I do not believe that this was an accident," Mary Ann Viafore told "48 Hours". "I'd like to see justice for Vinny. As I guess any parent would for their child."

She is now forced to honor her son's birthday at his grave.

"His birthday is August 22nd. He would have been 47 years old," she said standing at his final resting place. "His life was cut too short."

"...And I know that we'll see each other one day and I look forward to that day."

No matter how this plays out in court, Vincent Viafore's loved ones have vowed to keep his memory and spirit alive.

"We had so many memories together. ...Sometimes I just laugh to myself, you know, just thinkin' about him and just thinkin' about the fun times that we had," Parte said. "I feel, you know, happy that I got to have six years with him."

Angelika Graswald has been in jail for more than four months. Her trial is expected to begin in Spring 2016.

Graswald's family says they are giving their life savings to help pay for her defense.