In this video, our Chicago expungement lawyers discuss what type of marijuana drug charges can be expunged and how to do so. Under the new law some drug possession convictions will be automatically expunged. If you received a conviction for possession of up to 30 grams of cannabis and the conviction was not related to a more serious crime, your conviction is likely to be automatically pardoned and expunged from your record. If you have a conviction for possession of between 30 and 500 grams of cannabis or possession of drug paraphernalia.