There are many people, mostly drug mules that weren't necessarily even aware of what/how much they had been assigned to carry, that are serving life in prison.

There are many people, mostly drug mules that weren't necessarily even aware of what/how much they had been assigned to carry, that are serving life in prison. It's all based on how much they had on them and what type of drug, and much of it is arbitrary. For example, until 2010, the sentence for simple possession of a single gram of crack carried a mandatory minimum of five years, whereas someone found with 100 grams of powder cocaine would likely face probation.