Is fingerprint identification a science.... and can tiny fragments of finger or palm prints be reliably identified in accordance with modern legal and scientific guidelines?
It is scientific. 

Fingerprints have been collected, observed and tested as a means of unique identification of persons for more than 100 years. 

Scientists have proven the validity of fingerprint identification, including tiny fragments, in courts throughout the world for many years. 

The two basic ideas scientists believe about fingerprints are: 

  Fingerprints never change.  Small ridges form on a person's hands and feet before they are born and do not change for as long as the person lives. 

  No two fingerprints are alike.  The ridges on the hands and feet of all persons have three characteristics (ridge endings, birfurcations and dots) which appear in combinations that are never repeated on the hands or feet of any two persons. A ridge ending is simply the end of a ridge.  A bifurcation is a Y-shaped split of one ridge into two.  A dot is a very short ridge that looks like a "dot".

The basic fundamentals in the science of fingerprint identification are permanence and individuality.

 Permanence:  Fingerprint ridges are formed during the third to fourth month of fetal development.  These ridges consist of individual characteristics called ridge endings, bifurcations, dots and many ridge shape variances.   The unit relationship of individual characteristics does not naturally change throughout life... until decomposition after death.  After formation, an infant's growing fingerprint ridges are much like drawing a face on a balloon with a ball-point pen and then inflating it to see the same face expand uniformly in all directions.  Unnatural changes to fingerprint ridges include deep cuts or injuries penetrating all layers of the epidermis and some diseases such as leprosy.

Permanent scars, disease damage, and temporary changes such as paper cuts appear as jagged edges and sometimes "puckered" ridge detail in opposition to smooth flowing natural formations.  Warts can come and go, but generally push apart an area of friction ridges and can disappear completely when the wart is gone because they are not a part of the friction ridge structure.  Look at a wart with a magnifying glass and you will notice that the friction ridges "surround" the wart.  Senile atrophy of friction skin due to old age causes the ridges to often almost flatten, causing fingerprints with many creases (creases are also unique but not always permanent) and poorly defined ridges.   Oddly, newborn infants also often have more creases than clearly defined ridge detail in their barefoot prints.  The creases are unique, but change relatively rapidly and often disappear as the infant grows.  The best chance of seeing friction skin ridges on newborn infant footprints is to look carefully with a magnifying glass on and near the big toe.

Individuality:  In the over 140 years that fingerprints have been routinely compared world wide, no two areas of friction skin on any two persons (including identical twins) have been found to contain the same individual characteristics in the same unit relationship.  This means that in general, any area of friction skin that you can cover with a dime (and often with just a pencil eraser) on your fingers, palms, or soles of your feet will contain sufficient individual characteristics in a unique unit relationship to enable positive identification to the absolute exclusion of any other person on earth.  Recent studies comparing the fingerprints of cloned monkeys showed that they, just like identical twin humans, have completely different fingerprints.  When doctors state that twins have the same fingerprints, they are referring to the class characteristics of the general ridge flow, called the fingerprint pattern.  These loop, arch and whorl ridge flow patterns have nothing to do with the individual characteristics used to positively identify persons.  Before modern computerized systems, fingerprint classification was essential to enable manual filing and retrieval of fingerprints in large repositories.

For many years experts testified that no two fingerprints in the hundreds of millions of fingerprint cards on file in America had ever been found to be alike.  This was misleading in that large fingerprint files were for the first 110 years of police usage separated into small file categories by class characteristics such as:



  presence of scars

  presence of whorl, loop and arch formations in various fingers

  ridge counts and tracings between different pattern focal points (deltas and cores)

Thus, for example, at the FBI's former Identification Division with over 200 million fingerprint cards, no individual card and no individual fingerprint was ever completely compared against all the other fingerprints on file... just with corresponding fingerprint cards possessing the same class characteristics.  This all changed with the advent of AFIS (Automated Fingerprint Identification Systems) and many huge repositories have now compared individual fingerprints (such as just a fingertip from a crime scene) against every fingerprint in their entire database.  None have been found to have the same individual characteristics in the same unit relationship.

Math is the only exact science.  But, fingerprint identification lends itself well to mathematical validation and some AFIS (fingerprint computer) sites now make fingerprint card to fingerprint card positive identifications without human intervention.  Latent prints (finger, palm and barefoot) from crime scenes are not positively identified by computers, primarily because of background interference (dirt, scratches on items/surfaces touched, etc.) and the relatively poor definition of some crime scene latent prints.

When DNA evolved as a science, the term "DNA fingerprinting" was adopted to lend credibility to that science's newcomer status which is in its infancy compared with the empirical validation of fingerprint identification world wide.  DNA analysis as commonly practiced in forensic science laboratories cannot differentiate between identical twins, but fingerprints have always been able to differentiate identical twins.

Are fingerprints inherited... are they more similar between family members than between strangers?

Fingerprint patterns are inherited and thus non-fingerprint experts looking in a police fingerprint file must be careful not to confuse fingerprint records of close relatives based on fingerprint classification (Level 1 detail). Likewise, a National Crime Information Center Fingerprint Classification Code (FPC) may be very similar for close relatives. 

The actual finger and palm print detail used to effect an identification is not inherited and experts have no problem differentiating even identical twins.