Actually it’s a process a lot like putting together a jigsaw puzzle. You have the witness or victim start with the outline of the face (the edge of the puzzle). You work in from there. The victim/witness is provided with a catalog of facial components that breaks the face down into its various parts. Eyes, eyebrows, nose, mouth and so on. The catalog was compiled over many years by the FBI although I have also used another one from Miami-Dade P.D. In any event, after selecting the proper headshape, the most important thing for a victim/witness to do is place the eyes/nose/mouth in the right location inside the headshape. Believe it or not, if they get the location correct, the chances of them being happy with the sketch at the end is about 95%.
It is not so important that the victim/witness select the exact features, remember we are only trying to produce a composite that opens up leads, not a portrait that positively identifies someone. Once the headshape, eyes, nose and mouth are all satisfactory to the victim/witness, then it is really only a matter of filling in detail to their specification. This can be tricky with some but it should not obscure the face shape, and eyes, nose and mouth, or what we call the “Triangle of the Face”. Those three features are critical because short of plastic surgery, you cannot alter their appearance unlike shaving or clothing or jewelry.
Really any half competent artist can execute the sketch, the hard part is conducting the interview process, putting the witness/victim at ease and getting the most out of your people skills...
In portrait drawing we were taught that the eyes are in the middle of the head, half way between the eyes and the chin is the bottom of the nose and then half way between the bottom of the nose and the chin is the mouth.
That is the ideal and any thing that is different is what makes for your individual face. That is a simplistic explanation for what we were taught.
I would still like to have taken your class, it sounds fascinating.