Which factor is a mitigating circumstance for sentencing?

A mitigating circumstance is a factor that can lessen the severity of a sentence. In this case, the age of the offender at the time of the crime serves as a mitigating circumstance because younger individuals may be treated with more leniency in the legal system. This concept acknowledges that younger individuals often have a greater capacity for rehabilitation and may not fully understand the consequences of their actions. Courts frequently consider age in sentencing, particularly for juvenile offenders, recognizing that maturity levels can significantly influence decision-making and behavior.

The other factors listed typically contribute to more severe sentencing. Utilizing a weapon during the crime is an aggravating factor, as it poses a greater risk to victims and reflects a more serious nature of the offense. Prior felony convictions also generally lead to harsher sentences due to the offender's established pattern of criminal behavior. Similarly, a lengthy crime spree suggests a continual pattern of criminal activity, which often results in increased penalties. Thus, the age of the offender stands out as a factor that has the potential to reduce the sentence rather than increase it, making it the correct choice for a mitigating circumstance.