Body Ratios For Photo Elimination/Comparisons

by John Hodgden, Sr.
(Largo, FLorida)

I recently watched a CSI show where the length of one body part was compared to another limb and the resultant ratio was compared to the ratio's of the same body parts in a surveillance photo as a means to eliminate the subject as being the person in the photo.

Where do I find how this is done as I find myself in similar circumstances?