Defense attorney Patrick Lara told a courtroom in El Paso Yara Belen Perez, 30, never hit her daughter Jacqueline Gonzalez on the day of her death, the El Paso Times reported Wednesday.
Lara said the entire blame for Jacqueline's 2007 beating death belongs to Francisco Castaneda, Perez' live-in boyfriend.
Castaneda was convicted of capital murder in 2010 and sentenced to life in prison without parole.
Perez faces the same punishment if convicted at her second trial, which began this week.
She wept at Tuesday's session when prosecutors showed photos of her daughter's body in the trunk of her car.
The state's first attempt to try Perez ended in a mistrial after a juror overheard two deputies discussing a newspaper article about the case and relayed the information to other jurors.