In the case of a missing Texas mother of two who was found dead in Mexico last month with all her teeth removed, a medical examiner in Florida offered his perspective, telling Fox Nation host Nancy Grace on Tuesday that if she were alive when her teeth were removed, “This is probably one of the most painful procedures that you can do in terms of torture.”

“We use dental records and postmortem teeth X-rays to identify people, unidentify people all the time,” Dr. Tim Gallagher told “Crime Stories with Nancy Grace” on Fox Nation.

He added, “If you look at dental X-rays, each one of your teeth have very individualized characteristics that are custom just to you so if we can take the dental records from when they were alive and then take X-rays from when they are deceased and match up those teeth, all we really need are three to five points of uniquely identifying features to positively identify that person.”

Gallagher noted, “To have teeth removed forcibly … requires a great deal of force, especially in somebody young like this, [a] 23-year-old woman, so this was, if she was alive, this is probably one of the most painful procedures that you can do in terms of torture for her, so my heart actually goes out to the family and to her children because she had suffered so much.”

Lizbeth Flores left her home in Brownsville, Texas, on Aug. 9 to visit her boyfriend in the Mexican border city of Matamoros, her mother, María Rubio, told Telemundo 40 McAllen.

She crossed the U.S.-Mexico border through the Brownsville Veterans Port of Entry, according to the station. When Flores didn't return home, her mother reported her missing to the Brownsville Police Department the next day.

Mexican authorities found Flores’ body within the Matamoros city limits on August 11. Her body showed signs that she had been tortured, as it was covered in bruises and her teeth and part of her scalp appeared to have been forcefully removed, KRGV reported.

She appeared to have died from blunt force trauma to the head, consistent with a large rock found at the scene, authorities in the Mexican State of Tamaulipas told KRGV.

MISSING TEXAS MOTHER OF 2 FOUND DEAD, TORTURED IN MEXICO: AUTHORITIES 

Grace asked Gallagher if there was a “way to determine if her teeth were pulled out while she was still alive?”

“That's going be very difficult without somebody witnessing it,” he said in response. “As far as looking at the autopsy and looking at where the teeth were in the body, all we can say is that they were removed at the time of her death or around the time of her death.”

Grace then asked if Flores’ teeth had been removed after she was killed “as a way to keep her from being identified, would the gums have bled?”

“You can look at in the gingiva or the gums to see if there is any hemorrhage or bleeding that occurred there because she had a blood pressure,” Gallagher said, acknowledging that Grace’s point was correct.

“If a tooth is removed when the person is dead, then you will not have that bleeding around the gums and you could say with a great deal of confidence that that tooth was removed after they had expired,” he said.

Late last month a suspect had been charged with murder in Flores’ murder, according to New York Daily News.

The newspaper, citing Telemundo, said the suspect was identified by Mexican authorities as Braulio “N,” and was arrested at his home in the border state of Tamaulipas. Officials reportedly said the man lured Flores to Mexico to rob her.

Grace also interviewed former Drug Enforcement Administration (DEA) Senior Special Agent David Katz, who is now Global Security Group’s CEO, who offered general insight into what someone should do if a loved one is declared missing in Mexico.

“The Mexican authorities are not nearly as good, as professional as the United States authorities,” Katz told Grace.

He acknowledged that “it's a bit of a roll of the dice if you get the … non-corrupt law enforcement officer and sadly to say, there are fewer and fewer of those, then you have an opportunity to forward a case, but if you have somebody who … might very well be working for the cartel in the moonlight hours, then you're not getting anywhere.”

Katz said that the U.S. is “fortunate enough to have a good network of contacts down in Mexico,” who are “locals” and “know the system.” He went on to note that “the DEA has worked with them, sometimes to our dismay, but sometimes it works out very, very well.”

“So there are vetted units,” he continued, explaining that “they're checked,” “polygraphed” and “their reliability is assessed.”

“So those folks can be enlisted, but then again, you're dealing with an open area,” Katz said.

He noted that the U.S. has access to cameras and uses license plate readers.

“We have bridges, tolls and tunnels,” Katz continued. “Once you get into Mexico, you're losing a lot of that electronic tracking ability that we come to take for granted here in U.S. law enforcement.”

To hear more about this investigation and watch all of "Crime Stories with Nancy Grace" go to Fox Nation and sign up today.

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Fox News’ Danielle Wallace contributed to this report.