A crime scene is a dynamic work­space fret with chal­lenges and per­ils.  If the crime scene inves­ti­ga­tor is not care­ful, then the crime scene inves­ti­ga­tor can neg­a­tively impact the scene and com­pro­mise the phys­i­cal evidence.

We had exam­ined before the impor­tance of phys­i­cal and foren­sic evi­dence and how the the­ory of the Locard Exchange Prin­ci­ple plays into the crime scene as well as the need to prop­erly secure the crime scene to avoid alter­ing it and con­t­a­m­i­nat­ing the con­tents of the scene.

So, now that we have iden­ti­fied a poten­tial prob­lem, is there a poten­tial solu­tion or a way to min­i­mize the impact of it all?

There are two major math­e­mat­i­cal meth­ods that should be used in prop­erly exam­in­ing a crime scene:  The Carte­sian Coör­di­nate method (rec­tan­gu­lar), or the Polar Coör­di­nate method (circular).

This post will focus on the Carte­sian Coör­di­nate method.

The Carte­sian Coör­di­nate method is a coör­di­nate sys­tem for which the coor­di­nates of a point are its dis­tances from a set per­pen­dic­u­lar lines that inter­sect at the ori­gin of the sys­tem. A sys­tem for locat­ing and mea­sur­ing points in space based on a rec­tan­gu­lar coör­di­nate sys­tem with a  three dimen­sional axis labeled X, Y, Z.

It is using this math­e­mat­i­cal method to exam­ine, to mea­sure and to record the scene as we process it that allows us to be able to later extract the full mean­ing of the evi­dence col­lected.  It is a rela­tional con­cept whereby objects and evi­dence can be memo­ri­al­ized for its spa­cial meaning.

This method is usu­ally best used at a scene that has well defined bound­aries such as a room.

An exam­ple of Carte­sian or Rec­tan­gu­lar Coör­di­nate sys­tem used at a crime scene