[hguant]

The accused's criminal history comes up more in sentencing than it does in actual criminal cases - in the US system you're being tried on the crime before the court, not anything from your past. There are obvious exceptions - someone who is suspected of murdering their spouse who has prior domestic violence charges is one you see a lot - but in general, that comes up during the sentencing, where the judge has a lot of leeway to tailor the sentence to the circumstances.