Yes, mandatory sentencing would help deter criminal offenses, because criminals would know they would face a tough sentence if they offend. Too often, criminals talk their way out of sentencing with stories and excuses for their behavior. Mandatory sentencing creates more uniformity, and makes sentences more fair. Criminals will be more careful with their behavior, knowing that they face tough consequences.
Mandatory sentencing serves nobody in society, and only leads to the disenfranchisement of entire groups of people. Mandatory sentencing often leads to prison sentences that are completely removed from the severity of crime committed, especially taking into account the sentences of other, more serious crimes. There is no place in society for mandatory sentencing.