While the Bexar County District Attorney's Office recommended 40 years in prison for Harris, Judge Frank Castro said he may not follow the proposal because of the severity of the charges.
San Antonio police said Harris targeted women in Medical Center-area apartment complexes, with the first case dating back to March 2015, when Harris was 16.
During the time of Harris' arrest in June 2017, Police Chief William McManus said Harris would "pretend he was jogging through the complex" and attack women in their most vulnerable state.
Police said DNA evidence and then Harris' confession to the sexual assaults led them to charge Harris with first-degree felonies.
The sentencing for Harris is expected to be in late August.