Tactical crime analysts have utilized several methods, those highly refined and scientific and others flexible and intuitive, in detecting and analyzing serial crimes. However, all of these techniques were based on reliable knowledge of what the criminal had been doing. This may not always be enough. The analyst must know with some degree of confidence precisely how many crimes were associated with a particular series from the list of hundreds or thousands of similar crimes under consideration in the data. When it comes to identifying with certainty which cases were related and which were not, investigators and analysts had great difficulty, with the two biggest challenges being offender evolution (when the nature of a crime series changes over time) and reaction reflexes (where the offender's behavior changes drastically from one case to another). The combination of spatial and temporal idiosyncrasies relevant to each crime series, known as Spatiotemporal Profile, was identified as one of the most powerful techniques that can be applied to the problem of refining the series. The simplest spatiotemporal profile presented consists of three spatial factors, three temporal factors, and three combined factors. In addition, GIS allows tactical analysts to implement reliable and useful series-hunting refinement methods quickly and easily. In summary, no matter what methods used, it is critical for an analyst to not only detect a crime series, but define it clearly.