Greenville, Tex. (KXII) -- Arrest reports for sisters Stephanie and Shawn Flynn say baby Alexiana Stevenson was dead hours before police were called to the Prime Stop gas station on Monday around 11 a.m.
Stevenson was 54 days old.
Police report Stephanie Flynn, the baby's mother, used sister Shawn Flynn's cell phone to tell police the baby died in the backseat of her aunt's car on the way home from an overnight stay in Hugo, Okla.
Police said both sisters told the same story.
But investigators say that didn't make sense; The state of rigor mortis in the baby's body indicated the child had been dead for longer than the Flynn sisters claimed.
Rigor mortis is the stiffening of the joints and muscles of a body that occurs after death
So investigators asked some more questions.
After more questioning, police said the sisters admitted the trip to Oklahoma never happened.
Instead, Stephanie Flynn called Shawn Flynn on Monday morning from the metal shed she and the baby's father, Jeremy Stevenson, were living in and told her something had gone wrong and she needed help.
Shawn Flynn told police when she arrived both Stephanie Flynn and Stevenson were crying and told her the baby was dead when they woke up that morning and she needed to take her to the hospital.
On the way to the hospital, the affidavits say, Stephanie made up the story about driving to Oklahoma to visit an aunt.
Both women were arrested on evidence tampering charges for moving the corpse.
Stevenson was arrested in Fannin County Wednesday on a parole violation.
Autopsy results for Alexiana Stevenson are pending.