16 January 2018

What Should be the Alpha Level of the Criminal Justice System?

            Scenario: You are the child of a dictator who just passed away. In his passing, you have inherited full reign over a small nation. You have complete control over the state. Your father was a notoriously corrupt man who often abused his supreme power with no regard toward justice. You, being of a more moral mindset, have decided to use your reign to correct the injustices of your predecessor. Upon hearing this, one of your informants takes the initiative to enlighten you on the current state of the prison system. It seems that your father paid no mind to locking up “criminals” without trial or even evidence. For the right price, he would lock up the high school valedictorian who stole the rank away from your much more deserving salutatorian child. You are, of course, appalled to hear of this and demand forthright that the informant gather a report of every prison within the country’s borders.
            Some weeks later the report is finished and delivered to your desk. You peruse the results of the first prison. Without the need for a fair trial, proper procedures were rarely followed and it would be impossible to determine the innocence of any individual prisoner. However, based on jurisdiction information, an estimate of this particular prison as a whole was able to be generated and suggests an approximate population of 90% innocents to 10% criminals. Feeling for the lives that were torn away from these citizens, you decree to release all of the prisoners being held. You justify the release of the guilty by the overwhelming number of innocents who were wrongly convicted.
            You feel a brief dawning of hope for the new nation that you are building knowing how many citizens will be able to begin rebuilding their lives. You turn to the next section of the report and examine the results of another prison. Again, the evidence and reports needed to determine individual outcomes is absent but an estimate of the prison as a whole is given. This prison was split 50-50 of criminals and falsely convicted, law abiding citizens.
            What is your decree? Do you set them all free as before, or is freeing half a prison’s population of felons too great a cost? Regardless of your answer, imagine that as you continue through the various prisons in the report you are met with the same question every time, but of different proportions of guilty and innocents. What percentage of a prison would have to be innocent to justify letting the inverse of criminals free on the world.
            Statistically, we are discussing a number known as alpha. It is the probability a person is willing to make in a data analysis of making a type I error, that is, a false positive. In simpler terms, what percent of the time are you willing to falsely convict an innocent person in your criminal justice system. Of course, in research this number can be set, whereas in practice we can only estimate what has been established by the current laws and practices. However, I still find it an interesting thought experiment. So ask all of your friends, what prison would be your threshold? At what point would either alternative be equally appropriate within your own beliefs?


            -AMS

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