With many recent instances of police brutality coming to light, there has been much attention paid to the criminal justice system. Some call for a total rebuild of the police, while others suggest particular reforms at various steps in the process from crime to punishment, and some maintain that no changes are needed.
In this post I will analyze data from 22 police departments in major cities across the nation as well as national data from the Federal Bureau of Investigation to analyze the likelihood of “justice” in the event of two subsets of violent crime: homicide and assault.
To begin, I bifurcated the data into these subsets in order to provide more specificity in the analysis. For our purposes, we will pose a hypothetical in which a crime has occurred and “justice” will be defined as the arrest and conviction of the perpetrator. This analysis should provide a rough estimate for the question, “In the event of a violent crime, how likely is the perpetrator to be brought to justice?”.
So first, we can look at the nationwide clearance rate for each type of offense. The original data had varying categories describing outcomes for each reported crime, so it had to be standardized and grouped. I grouped each offense into one of two categories: either “Assault” or “Homicide”, and each outcome into one of three categories: “Open”, “Cleared”, or “Unknown”.
The charts below illustrate the results of the analysis. Throughout the country, the police are able to identify and arrest suspects in 76% of assaults, meaning about one out of every four never faces consequences from the criminal justice system.
Of those that are arrested, the Bureau of Justice Statistics reports that 45% will be convicted. Multiplying this probability with the “prior” indicated by the clearance rate we can see that 45% of 76%, or about 34% of perpetrators are brought to justice.
Looking now at homicides, we see slightly worse outcomes with a clearance rate of just over 60%.
Prosecutors fare better with the more serious of the two offenses, as homicide charges result in convictions 70% of the time. Calculating 70% of 60.6% yields about 42% of all killers brought to justice.
At this time I will reserve judgement for the reader. Given the likelihood that each crime results in an arrest and conviction, the question is… can we do better?
