Answer
Mitigating circumstances are those in Article 13 of the Revised Penal Code that reduce the penalty because they show a lesser degree of malice or perversity in the offender. They include an incomplete justifying or exempting circumstance; the offender being under eighteen or over seventy years old; the absence of intention to commit so grave a wrong; sufficient provocation or threat by the offended party; immediate vindication of a grave offense; passion or obfuscation; voluntary surrender; voluntary confession of guilt before the prosecution presents its evidence; physical defect that restricts the offender's action; illness diminishing willpower; and analogous circumstances.
Mitigating circumstances may be ordinary or privileged. An ordinary mitigating circumstance, if not offset by an aggravating one, lowers the penalty to its minimum period (Articles 62 to 64). A privileged mitigating circumstance — such as minority, or an incomplete self-defense with a majority of its requisites — reduces the penalty by one or more degrees and cannot be offset by any aggravating circumstance.