I feel sorry for police sketch artists because they're snubbed by other artists. Artsy-type artists simply can't see the art in the kind of flat, symmetrical faces that you see on wanted posters (above). That's too bad because the artists who do the posters are often more skilled than you'd think, they just work in a medium that's deliberately designed to look clunky.
This (above) is, believe it or not, the most useful kind of police sketch. It's not pretty, but it wasn't meant to be. It's intentionally crude, emphasizing only the few bits of information provided by the witness, and adding nothing. It gives the officer on the street lots of room for interpretation.
What you don't want is a sketch that's too specific (above). It may look good, but a face that's too detailed will lead to a search for that exact face, and no other, which is a mistake. It's impossible to derive a true likeness from the limited information given by witnesses. An artist has to resist the temptation to fill in a drawing with made-up detail in order to make the sketch look pretty.
A witness description that says, "He was a blonde with wire-frame glasses" is almost useless, since glasses can be discarded and hair can be dyed. A trained police artist listens for details that are hard to fake, like the shape of the jaw, the cheekbones, and the size of the eyes, nose and ears. Sometimes glasses are only sketched lightly and hair is made to deliberately look fake so the viewer can imagine the face without it.
A good police artist is a good interviewer. He knows the questions to ask which will spotlight the details he's interested in.
It's predicted that computer programs will gradually replace sketch artists, but it's been slow in coming. That's because computer sketches are too specific. You end up looking for that exact face to the exclusion of other similar types. The common programs are Faces 4.0 and Smith & Wesson's Identi-Kit 6.0.
