Recently I was searching around for publicly available police data and found that a surprising amount of data is available to the public. Often it is very portable, letting the curious download raw data from government systems. Many cities have built out API’s so you can get live feeds from their systems. I found a treasure trove of raw arrest data from the City of Baltimore. Like a lot of cities, they have exposed their database of arrests to the public. The data only goes back to the beginning of 2013, but that’s a lot.
Since the first of day of 2013, Baltimore City police have made 152,103 arrests as of September 30th, 2017. That works out to an average of 87 arrests per day. That does not sound like a big number, but according to studies, the average time awaiting trial is close to 40 days. The number of people being held in the city awaiting trial is about 8,000, on average. Put another way, about 1.3% of the city’s population is held at any one time, awaiting their turn in the criminal justice system. That does not included convicts.
Of course, the break down by race is what you would expect in Baltimore.
Interestingly, there were only 1428 arrests for murder and attempted murder. They don’t code the crimes in an easily understood way. I simply searched for all arrests containing the word murder, which included attempted murder. Netting out the lesser charge and the total is just 252 arrests for the crime of murder. In the same period, 1382 homicides were committed in the city. It appears arrests for attempted murder is where they start with murder cases. That or the murder total would be much higher if the locals had better aim.
Here’s the racial break down of murder related arrests.
The black share of arrests for murder related offenses should be viewed in addition to two other statistics. Baltimore is 63% black according to the last census and 29% white. This means that blacks are over represented in the arrest data for murder related crime. Whites are under represented. It should be noted that Hispanics are counted as white, but the city has a small Hispanic population. Even so, whites are significantly under represented. This is a pattern that turns up in all homicide studies, even in majority black cities.
The other factor is the victimization data. Murder is almost always a personal crime so the murderer usually knows the victim or they live in the same area. Even in a city like Baltimore, where one block can seem like a different country from the next block, most violent crime is personal. That means most times, the murderer is of the same race as the murdered. Looking at the victimization data, the number of black murder victims over the same period tracks the arrest pattern, as far as the racial breakdown.
Here is the racial break down of the murder victims.
The victim numbers let us net out the Hispanics from the white total, but Baltimore does not have a big Latino population, so the numbers don’t change much. Given the white flight to the suburbs, the city’s white population is probably closer to 25% in this time period, but the white crime share is around 5%. On the other hand, Blacks are 65% of the city’s population and 90% of homicide related crime and over 80% of all arrests. Put another way, if you removed the black population, Baltimore would resemble Salt Lake City.
Finally, here are the arrests by age.
Here’s the arrests by interesting cohort.