Monday, November 21, 2016

Introduction to Link Analysis: Part 1 Time Event Charts

I originally wrote this post for a software company’s blog in 2014. This company was bought out and recently their blog and website have been removed from the web permanently. I am reposting it here for posterity. 

Most of the posts that I have done for are related to the field of Crime Analysis. The next couple of posts are going to deal with a topic that more rightly falls into the field of Criminal Intelligence Analysis. Where crime analysis more often deals with the numbers of reported crimes, criminal intelligence more often deals with information from human sources. In spite of this difference, by practice most crime analysts end up doing some of both fields. The criminal intelligence analysis task probably most often asked of crime analyst is performing Link Analysis.

We’ve all heard the old saw “A picture is worth a thousand words.” While it might be an old saying, there is a lot of truth in it. Often times a picture or diagram can explain something far easier that words. The football coach who uses a diagram to explain a complicated play during practice does so because it’s much more effective than trying to explain it with words alone.

Link Analysis diagrams are used to explain the relationships between entities in a criminal investigation.

The analytical tools and techniques used in Link Analysis can help you to understand the complex group of facts that is the case you are working. Many times, the cases we are assigned to investigate are pretty simple and don’t require us to use Link Analysis tools to understand them. However, there are times we’re assigned one of those huge complicated cases that end up filling up file boxes with documents. Even if you’re the case agent the sheer volume of information can be hard to keep up with, much less explain to your supervisor or a prosecuting attorney. It’s these types of cases where Link Analysis tools really shine.

Link Analysis Tools

There are a number of tools that are used for link analysis. Some analysts include flow charts as a link analysis tool but others do not. The same goes for Time Event Charts. I am not going to include flow charts in this series of posts. The tools I will discuss are:


  • Time Event Chart
  • Association / Activity Matrix
  • Link Analysis Diagram


There is nothing really magical about these tools. Often times, investigators view them as some sort of mysterious mojo that an analyst cooks up over a steaming cauldron while muttering incantations. These analytical tools can only help you arrive at a solution. They will not determine the solution for you. The most important tool is you, a seasoned analyst with your judgment and wisdom. As the authors of an US Army manual said about link analysis tools “The techniques themselves are not the solution. Don't let the tools drive the problem.”

Let’s look at the first Link Analysis tool.

Time Event Chart

A Time Event Chart records events temporal relationships. In other words, it’s a diagram that represents events in a chronological fashion. Time Event charts can display events spanning long periods of time in a reasonably compact fashion. Often times, criminal conspiracies include relevant events spanning several years. Events that are relevant to proving a conspiracy may include preparatory events as well as the actual crime itself. Knowing how these events interrelate is important to gaining a complete understanding of the conspiracy itself.

The first, and sometimes last, event in a Time Event Chart is displayed with a triangle. You may wish to avoid using a triangle for the last event on a chart unless it’s a concluding event such as an arrest. If you prepare a Time Event Chart for an ongoing case, don’t worry about the last symbol being a triangle, you may have more events to plot as your case grows.

Successive events in a Time Event Chart are represented by a rectangle. You should note information such as the event date, case number or a brief description of the event the symbol represents. A particularly significant event can be highlighted by drawing an X through the event node. The flow of time in a Time Event Chart is symbolized by arrows.

A simple Time Event Chart is depicted below.


A variation on the Time Event Chart includes the days between events on the arrows between event nodes. This may assist you in determining a temporal pattern to your series of events.

We’ll look at ways to draw these diagrams in a subsequent post. However, the drawing tools built into Microsoft Office work really well for these charts, especially the Time Event Chart.

Next week we’ll look at Association / Activity Matrixes.

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