Two family members testified that growing up, Aguirre was friendly and helpful and they said they were astonished to hear the accusations of torture and murder against him.
"I couldn't believe it," said Luis Marin, Aguirre's younger cousin.
Marin said he believes there is humanity in his cousin and his life is worth saving.
He recalled when they were younger, they would go to the movies together and Aguirre would pay for the tickets and candy since they were both working.
Later when Marin got married, he said Aguirre paid for the down payment on the first apartment he moved into.
Marin also recalled a time when Aguirre acted "heroic" to protect his sister who was being bothered by a man at a festival.
The prosecutor asked if it was "heroic" to beat and torture a child to death. Marin responded no.
Last month, Aguirre was found guilty of first-degree murder in the death of his girlfriend's 8-year-old son, Gabriel Fernandez.
During trial, prosecutors presented a long history of abuse against the boy committed by Aguirre and allegedly by the boy's mother, Pearl Fernandez. That included shooting him with a BB gun, feeding him cat feces and forcing him to sleep while gagged and bound inside a small cabinet.
Gabriel died in May 2013.
Pearl Fernandez is to be tried separately.
Another witness called for the defense, William Adams, is a consultant on prison system issues who formerly worked for the California Department of Corrections and Rehabilitation.
He said as someone in the state correctional system convicted of killing a child, Aguirre would be targeted by other inmates and "his life would be in danger."
"They have a very, very, very low regard for anyone who has committed a crime on a child," Adams said.