On Tuesday - coroners in Wyoming gave followers of the Gabby Petito case an answer they'd been waiting for: the 22-year-old from Long Island was choked to death.

Teton County Coroner Brent Blue made the determination weeks after they ruled she died in a homicide and even narrowed down the window for her death, stating that her body had been out in the elements of Grand Teton National Park for three to four weeks before it was found on Sept. 19.

But - there's still a lot we don't know. Chief among those questions: who killed her? Right now the only person of interest in the case is her former fiancé, Brian Laundrie, who has been on the run for nearly a month now.

That question is unanswerable at the moment, but others — especially those about the autopsy — might have an answer. That's why on this week's episode of The Debrief, investigative reporter Pei-Sze Cheng sat down with Professor Joseph Scott Morgan, a forensic expert and former medical examiner teaching at Jacksonville State University in Alabama.

Download this week's episode of The Debrief on Apple Podcasts, Stitcher, Spotify or wherever you listen.

This transcript has been lightly edited for clarity and concision.

Pei-Sze Cheng: What do you think was most important about what he said, Joseph?

Joseph Scott Morgan: When he had the press conference (on Tuesday), Dr. Blue actually stated that Gabby's death, the cause of death was asphyxia. A sphyxia is a very broad term. It can come from everything from suffocation to strangulation, to ligature strangulation and even compression to a certain degree.

But let's back up just a little bit and think about the manner. The day that they did this autopsy, they couldn't get out the door quick enough that afternoon to give us the manner of death. There's five manners of death. And when they shot out of there, they specifically said, "This is a homicide."

That's very powerful, and I'll tell you why. To rule something as a homicide -- and the purest definition literally means "death at the hands of another" -- they saw something so glaring. Even though Gabby had been down three to four weeks, they were able that afternoon with no further testing to say, "this is a homicide."

The problem arose -- for us on the outside, not only inside -- it lacked specificity. That brings us to the cause that he came to on Tuesday. And initially, you know, I kind of interpreted as him being a little bit coy with reporters.

But then last night, something huge happened. Dr. Blue gave an interview with Anderson Cooper. And on that show, he stated that not only was this an asphyxial death, but it was a strangulation via a throttling. That really narrows the field down because throttling is so very specific.

He went to great lengths to even say that this was not mechanical, which essentially means that there wasn't a ligature involved. When they say throttling, they're talking about the application of two hands on this young woman's throat.

And most of the time in the classic sense, when you're talking about throttling, it can happen either anteriorly -- that means from the front -- or posteriorly. We think about movies where some stranger walks up and they choke someone. But this isn't the movies.

My opinion is that this is a face-to-face event. This is very intimate. Anytime you have an asphyxial death, it's one of the most horrific things that can happen because there's literally less than a foot of clearance between the perpetrator.

He would have looked her in the eye and as he's literally squeezing the life out of her. So the bigger question is, and we don't have an answer to this yet. What exactly did they see specifically?

Well, we had obtained a document via a Freedom of Information Law request from the Teton county coroner's office that confirmed that her manner of death was manual strangulation slash throttling. So manual strangulation would mean that there was no other instrument involved. Is that what you were just saying before?

Absolutely right. If you take like a rope and you apply it to a surface, it's going to leave a specific mark and it'll have defined margins to it. It won't expand out with a manual strangulation.

Think about the surface of your hands. They apply pressure over a large area. I can't speak to this one particularly, but I've seen cases involving throttling where you'll have widespread and diffuse hemorrhage throughout the musculature. Sometimes you'll see it externally, but let's remember Gabby's been down for a while so I don't know if they could see that.

But when they were able to do a deep examination, they very well may have seen into the musculature little focal areas of hemorrhage that were broad-ranging.

And there's something else that comes into play here. It's not just the hemorrhage that we're looking for at autopsy. We have our trachea right in the center of our throat. It's cartilaginous and can actually fracture when you apply pressure to it.

There's also the infamous hyoid bone. It's located way, way up in your throat. Many times with manual strangulation, you'll see a fracture in the hyoid as well. It is very rare that this bone gets fractured when manual strangulation is not involved. You don't see it most of the time in hangings, you don't see it just as like an accidental event. It just doesn't happen most of the time. It's direct application of pressure on this specific area.

So many people have been asking this question: if they were able to identify this as homicide so quickly, what took them so long to come to this autopsy ruling?

The coroner has been talking to the authorities. People say, "well, Morgan, obviously he has." Now what I'm saying is he's communicating with them. The authorities were at the autopsy. I can almost guarantee an FBI evidence response team was there.

This is an FBI case. They are not going to reveal any further information specific to the kind of the causal factors. The Feds tend to play things very close to the vest. So they're not going to release a lot of information.

I'm surprised that we got what we did, but let me tell you what they did that was kind of cool. Dr. Blue said we did a CAT scan and not just a CAT scan. We did a full body CAT scan. Most coroner's offices might do an X-ray if they have access to an X-ray. He did a CAT scan.

Why is that so unusual?

Because it's high-end equipment. Not everybody has this.

But the bigger point here is that with X-ray you take a case now that's being documented in a two dimensional, perspective. Think about anytime you've ever seen a personal X-ray, you'll look at it and say, "what is this? I can't make heads or tails out of it."

Now you go CAT scan, you're talking three dimensional. Now you can appreciate height and depth and thickness and all those sorts of things. And this is a powerful tool at trial. One of the biggest things that happens with autopsy photography for instance, is that the defense will say, "this is too graphic. It's prejudicial. We can't show this to the jury."

There's nothing prejudicial about CT scans. It's not gory, but you can appreciate say for instance, before you ever do the autopsy, the body's completely intact. You can appreciate the status of the hyoid bone in relation to any hemorrhage that might be there. You're not disrupting the body at all, but it's demonstrative and that's very, very powerful.

They went to great lengths in this autopsy. He's also submitted trace evidence, according to what he said there's an entomologist involved, which is a bug doctor. There's also a forensic anthropologist who deals with skeletons. It's a real full court press that they're putting on. And at the end of the day, I can tell you they are going to have a boatload of evidence that will be tied up in a very neat package.

Well, let's talk about this evidence. They said they retrieved DNA evidence, but won't it be tricky to use this in court because Brian and Gabby had been in a relationship?

And we don't really know what the status of the DNA evidence is because you can't just look at a body with the unaided eyes and say, "okay, there's DNA evidence. I'm going to collect it." They could have taken a sample from her, submit that as DNA, to the point of exclusion.

Here's what's key though. You remember what I said about manual strangulation? It's a very personal event.

I mean, it is the most intimate of homicides that can occur. It's a primal response to fight somebody off. If you're being choked or being strangled.

My thought is this. They have done nail scrapings and probably nail clippings. And if folks will essentially look down the long axis of their fingernail and you see how curved your fingernails are. Essentially when you scratch, that's not just passive DNA, we're not talking about sharing a space with somebody where his DNA gets on her and all that sort of thing. We're talking about curled up skin, tissue, blood that's protected beneath the nail.

And that takes this up to another level. How's the defense explain that away? How can they actually say, "for good reason she would have his tissue beneath her fingernails."

That's not something that would happen in the normal course of life, like touch DNA, where we slough skin cells and they fall away. That's not what we're talking about.

And then your experience, um, you know, testifying in these cases, the person that strangles somebody to death, who is that person usually?

In my experience and also teaching that university like I do, we talk about intimate violence. You're more at risk of losing your life to somebody that you know in your circle, as opposed to some stranger. That's Hollywood fiction. It happens, but it doesn't happen to the level that domestic disputes happen to end in some kind of fatal event.

That's what you're looking at. It's intimate, personal person violence.

Right now, Brian Laundrie's the only person of interest in her disappearance. He is wanted on a federal arrest warrant for bank fraud. Both attorneys admitted that he took money out of her bank account. How bad do things look for Brian Laundrie?

Let's just play a game and say, are we aware of any intimate friends that Gabby Petito had in Wyoming? I'm not. Is there anybody in Wyoming that held a grudge against her? I guess you could say that some mysterious stranger came out of the dark and perpetrated this crime.

But remember what I just said about intimate one-on-one crimes, they require this passion-driven thing that's going on. Who would dislike Gabby Petito so desperately in one of the most isolated places in Wyoming to wrap their hands around her throat and choke the life out of her?

That's the question that needs to be asked now, I don't know what the status of Mr. Laundrie is, other than the feds are looking for him.

But I know this, when they filed those charges relative to this bank transaction, the Feds did something really interesting. People have talked about those charges as being kind of innocuous that sort of thing. It's not.

Once they flip the switch on, they then invoked the power of the US Marshal Service. They're looking for him actively. They go hunting for people that are on the loose.

So he's got the full of the Feds bearing down on him, wherever he is and whatever context he's in right now, I have no idea. But suffice it to say, they're going to look under every rock they can.

Is there anything about this situation that helps Brian Laundrie?

I guess there could be room for reasonable doubt because he's made herself scarce and he's lawyered up. That's the biggest thing in his defense at this point in time, he hasn't said anything. I mean, It's very frustrating for everybody in the public. But in our country we have a right to remain silent and he's chosen to do that. I think that's the biggest mark for him.

I think that right now there are people all over this country that are making judgements about this case. This case is on the radar in Wyoming. Trust me, they don't have a huge populace out there. They're aware of it. And so anybody that might be on a jury, they're watching this, they're reading this in their papers and watching the news over coffee every morning.

They're talking about it. Things like this, they happen but they don't happen like this.

Certainly the glaring light of the media doesn't show up and look high marks to Dr. Blue. He's never had this kind of spotlight on him. Wasn't it really, really interesting when he actually made that comment as a coroner about domestic abuse?

Did he give anything away? He basically said that Gabby was a victim of domestic violence.

That was striking to me. He was so coy with everything else. You didn't expect that utterance to come from a coroner. It really gave an insight into his communication with anybody else that's involved in this case. Trust me, they've been talking.

There's something else that he did as well. He narrowed down that date when she was last seen.

The last time she was known to be with him was on Aug. 27. It's later that day, where the vloggers see Gabby's van parked over in the campground. It's the same day and it's only 31 miles away. Out there, 31 miles is a very short distance.

And so they would have covered that distance and that's the last time that they really know. He made some mention of Aug. 29 or Aug. 30, and so automatically that kind of narrows it down.

And in a case like this, where you have a body that is decomposed it's very difficult to narrow this time frames down. We traditionally can't do better than a week, most of the time, but he really kind of revealed a bit of insight in that respect as well.