Tanner Horner's grandmother is testifying in his murder trial sentencing

Tanner Horner's defense attorneys called his grandmother to take the witness stand Thursday afternoon as they continue to make their case to a jury to spare Horner from the death penalty.

Horner's mother testified last week, telling the jury about her own struggles with drugs and spending parts of Horner's childhood in jail. Her parents, especially her mother, took a major role in raising Horner.

Horner's grandmother is the latest in a string of defense witness who have testified about Horner's difficult upbringing, which also includes Horner's former teachers and childhood friends.

In addition to his family situation as a child, Horner's lawyers have presented evidence about his autism diagnosis, struggles with mental health, lead exposure and issues with his brain development in order to convince the jury to sentence him to life in prison instead of death row.