A married couple accused of murdering and setting fire to the body of Christy Lynne Espinosa told investigators a variety of stories about her death, and each blamed the other, according to arrest affidavits released Tuesday.

The consistent part of their stories is that the three drove around Travis County drinking late on the night of a Mardi Gras celebration on Sixth Street, according to arrest affidavits.

But officials said the details kept changing, and included statements that Espinosa died accidentally, that she was killed to steal her identity and that she was killed because she flirted too much with the husband, who was driving the car.

Murder charges were filed Tuesday against Martha Medina-Hernandez, 26, and her husband, Kenneth Hernandez, 33, Travis County sheriff's office spokesman Roger Wade said.

The body of Espinosa, 21, was found burned in a field near the 6000 block of North Imperial Drive in eastern Travis County on the morning of Feb. 25. She was last seen during Austin's Mardi Gras celebration.

Medina-Hernandez was previously a "person of interest" in the case, officials said. She was picked up in Eagle Pass on Sunday on unrelated charge of aggravated assault with a deadly weapon. Hernandez was arrested Tuesday, Wade said.

According to an arrest affidavit, Medina-Hernandez's ID was found several feet from Espinosa's body. Tests by the Travis County medical examiner's office concluded that gasoline was used to ignite her body, the affidavit said. An autopsy revealed that she died before the fire was set, and suffered a bruise on her neck before death.

Medina-Hernandez and her husband told investigators a number of conflicting stories about how the death occurred, according to the affidavit.

After finding Medina-Hernandez's ID at the scene, investigators located her husband and questioned him. He said he had not seen his wife recently, and when he called her in front of investigators and told her he was with the law enforcement officers, she hung up, the affidavit said.

Investigators then spoke with Espinosa's boyfriend, Michael Stackable, who said he went downtown with her to celebrate Fat Tuesday. She was asked to leave the Ivy Lounge, where Stackable worked, because she was intoxicated, the affidavit said. She left for the nightclub Fuel with three women, Stackable told investigators, according to the affidavit.

After being arrested in Eagle Pass, Medina-Hernandez was questioned by investigators on March 8. Although she initially denied any knowledge of Espinosa's death and couldn't explain why her ID was at the crime scene, she said she met Espinosa with her husband downtown, according to the arrest affidavit. They went to a bar on Sixth Street and left in a white Honda Civic, drinking liquor in the car, she told investigators.

Medina-Hernandez then said Espinosa fell asleep and wouldn't wake up, and they believed she was dead, the affidavit said. Medina-Hernandez said her husband feared losing his job at Capital Pediatric Group, and they went to a gas station in Del Valle and filled up a can with gasoline.

She said they drove north to Imperial Drive and lit Espinosa's body on fire, disposed of their clothing and went to pick up their son, according to the affidavit.

Investigators met Hernandez at the home of his sister, where they said he told them a different story. He said that while they were downtown, Espinosa was flirting with him, which made his wife jealous, the affidavit said. He told investigators that Medina-Hernandez used plastic-type "Saran Wrap" to reach from the back seat and suffocate Espinosa, the affidavit said. He said his wife forced him to buy the gasoline, then she lit Espinosa's body on fire, the affidavit said.

Medina-Hernandez was interviewed again, and she gave another version of events, investigators said. She told investigators that they drove around drinking with Espinosa because her husband wanted to have a "threesome," the affidavit said. Because Espinosa was unconscious from alcohol, Medina-Hernandez denied his request.

She said her husband became upset, and ordered her to suffocate Espinosa with her hands, the affidavit said. She let go and Hernandez finished the job with his own hand, she said. After that, Hernandez burned Espinosa's body, she said.

Hernandez's sister Rebecca told investigators she went to pick up Medina-Hernandez in Mexico. Medina-Hernandez told Rebecca that she used Saran Wrap to kill Espinosa to steal Espinosa's identity, the affidavit said.

Medina-Hernandez told the sister that she needed to go to Mexico to visit family but couldn't do so with her active arrest warrant, so she wanted Espinosa's ID, according to the affidavit.

Medina-Hernandez told Rebecca that she left her ID next to the body so police would think Espinosa's body was hers, the affidavit said.

The arrest affidavits accuse Medina-Hernandez and Hernandez with placing their hands or other objects over Espinosa's mouth, killing her with asphyxiation, and lighting her body on fire. Bail was set at $250,000 for each.