In most instances there are unique circumstances and/or personal characteristics that are deserving of consideration as mitigating factors. This often necessitates providing additional relevant background information to ensure the judge is fully informed and understands the mitigating nature of the identified factor.
Particularly with federal cases, but also with many state cases, associated case law is researched and presented as mitigating considerations. Case law, in particular, can be a time intensive task in matching common ground with your particular case and issue.
Additional research is required in federal court cases to identify the sentences imposed in similar cases to ensure the recommended sentence does not create a disparity with other similarly situated defendants. Research in federal cases also helps in the identification of other 3553a factors that are relevant to your case.