If nature had only one fixed standard for the proportions of the various parts, then the faces of all men would resemble each other to such a degree that it would be impossible to distinguish one from another; but she has varied the five parts of the face in such a way that although she has made an almost universal standard as to their size, she has not observed it in the various conditions to such a degree as to prevent one from being clearly distinguished from another...~ Leonardo Da Vinci 

Forensic art is any art that aids in the apprehension or conviction of a criminal offender, or aids in the identification of unknown deceased persons. It is primarily used to present visual information to aid law enforcement in focusing on a suspect's appearance through a witness' description.

There are four categories of forensic art including: 

Composite Imagery
Graphic images composed of individually described characteristics of the human face (may also include full body drawings or objects). This category includes images drawn by hand; computer generated images and/or "Identi-KIT" composites. 

Image Modification/Identification
Methods of manipulation, enhancement, comparison and the categorization of photographic images. This includes age progression and fugitive update drawings. 

Demonstrative Evidence
Visual information used for court purposes (Trial displays) can be computer generated or sketched by hand. 
Reconstructive/ Postmortem Drawings
Methods of identifying human remains in various conditions of decomposition. These include 2-Dimensional and 3-Dimensional facial reconstructions from the skull as well as sketches and computer generated images.  

Most often the Forensic Artist is called upon to interview a victim or witness on the description of a suspect from a crime in which there are no other leads. The artist interviews the victim/witness on the various features of the face. The artist documents these features and creates a two dimensional likeness of the suspect involved in the crime. 

The composite image can also include objects such as tattoos, clothing, vehicles and jewelry to aid in the investigation. The law enforcement agency then works with the media and other agencies to circulate the composite image to the general public to generate tips as to the identity of this suspect. The composite sketch is often an important tool in the investigation. 

Forensic Artists may also be called upon to assist with a post mortem drawing or facial reconstruction from the skull, a combination of art and science. This is done when human remains are recovered and no identification of the body has been made. The Forensic Artist can be an important link in finding a name for the missing person’s databases to search.

The identification can then be positively made by DNA or dental comparisons. There are two main ways of reconstructing the face of a person when you only have incomplete remains to go on. One way is to create a three dimensional reconstruction using clay. The other is to use computer technology to create a two dimensional picture based on the remains of the skull.  Whichever technique is used, putting flesh on the bones is always a combination of detailed forensic science, careful archaeological method and artistic imagination.Using Computer 2D Technology 

The Forensic Artist must first make the determination from the condition of the remains to do a postmortem drawing from the morgue photos or a two or three-dimensional reconstruction of the face from the skull. As much of the skull as possible is needed to be assembled. This can be painstaking work that involves piecing together tiny fragments of bone. The postmortem drawing would be done if there was enough of the soft tissue still left on the skull. In most cases where the body is badly decomposed, a facial reconstruction from the actual skull would have to be done.  

Step 1: This is the technical phase of the reconstruction. Vinyl eraser strips are cut to the exact length (in millimeters) according to the tissue depth date chart appropriate for the individual: these give an idea of the depth of the flesh at different positions on the skull. The tissue depth data chart is compiled from a study done on the tissue depth of cadavers done by Rhine and Campbell in 1980. The study took into consideration the thickness of muscle, fatty and connective tissue and skin thickness at a particular morphological landmark on the skull. 

The tables are prepared for Native Americans and persons of Asian descent, African-Americans or persons of African-derived heritage and American Caucasoid, or persons of European descent. The tables are further divided by slender, normal or obese groupings as well as by the sex of the individual. The tissue depth markers are then glued to the skull at the appropriate anthropological landmarks using a cement glue, which is later removed with acetone. The skull is then photographed, taking care that it is set in the Frankfort Horizontal (a position attained by placing the bottom of the eye-orbit horizontal to the top of the external auditory meatus or bony ear hole) so that there is no perspective distortion. The photograph is then printed in one-to-one prints or life size enlargements. 

Step 2: A piece of opaque paper is placed over the print of the skull and the artistic phase begins. This deals with the development of the individual features upon the face. The tissue depth markers act as a guide to the contours of the face. A careful study of the muscle attachment sites on the skull and the subtle asymmetries of the face should be made while creating the drawing. The skull is used as a template for the sketch drawn upon it. The position of the eye-orbits, nasal aperture and position of the teeth create perfect and pre-determined proportion in the finalized drawing. 

Step 3: The final drawing rendered from the photograph of the skull can then be released to the media and police agencies for the identification of the victim.A composite sketch is an artistic rendering showing a likeness or similarity of a person or object, and is not considered a portrait of an individual. Instead, it is a two-dimensional record, or impression, of someone's memory. It is considered a tool of identification, elimination and corroboration. Some of the major uses of a composite drawing are to record the memory of a witness or victim through artistic interpretation. The completed drawing may then be recognized through other people leading to an identification of the suspect. It also aids in eliminating other suspects who do not resemble the composite, and may strengthen a witness's statement. Also, during the time the drawing is being made, the witness may recall other valuable information for the investigator. Interestingly, a composite drawing is not restricted to pictures of people. A drawing can also include descriptions of weapons, jewellery, vehicles, tattoos, clothing, and artifacts.