A grand jury last week indicted the 55-year-old Matallana-Galvas and 47-year-old Torres-Sanchez on charges including felony second-degree murder and robbery, and misdemeanor practicing medicine without a license.
Police arrested the pair at McCarran International Airport on April 9, hours after Elena Caro's death.
Police say the couple gave the Las Vegas woman a buttocks injection because she wanted a shapelier figure. Authorities say the procedure took place in the back room of a tile business.
Caro was later found walking the streets in agony. She was taken to a hospital, where she died.