Crime Prediction – Predictive Modeling in Law Enforcement

No predictive model is going to be 100% accurate unless by chance.  The nature of predictive modeling is to learn from the past and see into the future.  Essentially, predictive modeling is just modeling.  Think about why we use statistical models – so we can fit the data into a pattern of behavior and anticipate future results.  It’s all about how you use and interpret this model.

 

Crime analysts may use a tool similar to the following example on a robbery series:

 

Data

Date DOW DBO Time Location Money Stolen
3/1/2005 Tue 18:30 1502 E Broadway $1,120
3/8/2005 Tue 7 17:25 1454 S Main St $1,130
3/12/2005 Sat 4 19:00 1903 S First St $1,370
3/17/2005 Thu 5 20:00 1989 N Fourth St $1,420
3/24/2005 Thu 7 20:25 1048 N Third St $1,700
4/2/2005 Sat 9 21:45 1336 E Kimberly Ave $980

 

Average 6 20:09
Minimum 2 17:18
Maximum 9 23:47
St. Dev 1.91 1:36

 

Predicting Next Hit

Min Earliest 7/14/2005 17:18
1 St. Dev Earliest 7/16/2005 18:33
1 St. Dev Latest 7/20/2005 21:45
Max Latest 7/21/2005 23:47
Correlation 0.79381602
Slope 0.00588819
Y-Inctercept -1.231583
# of Days til Next 3.18
Predicted Date 7/15/2005

 

Based on the frequency of the robberies and the amount stolen, the next predicted date is in 3.18 days.  Now, would you tell your patrol officer that they can expect another hit in exactly that time?  No.  But you can use this information to provide a possible date range.  You can also provide the most likely time for a robbery to occur.  Past data helps us to identify patterns for the future but it is not always the rule to follow for future events.  This data is used in conjunction with intelligence reports from patrols.

 

See the Resources page for other templates like this one this template on Robbery Series.

 

Data is concrete.  It gives us the probability of future events occurring.  Add in variables that you know will affect the probability, and you have a predictive model that is even less concrete.  Explaining this to your “customer” should go something like this:

 

This is what happened [insert data here].  This is the probability of it happening again [insert probability here].  Based on the pattern, the next most likely event occurrence is [insert data range]. 

 

In conclusion, it’s all about conclusions.  You will not be able to give a definite “next step”, though you can come pretty close.  A marriage of data analysis and intelligence analysis will give you a higher probability of catching and preventing criminal actions.