Fingerprint a myth or reality
All of us know that fingerprints are used for personal identification for more
than 100 years. It is the simplest and inexpensive method of identification.
Fingerprints are the forensic scientist’s handiest tool to catch criminals,
helped law agencies and produced as evidence in law of court.
What make Fingerprint science special?
Without the support and assistance of hand, no crime can be committed.
The chances to find fingerprint marks are higher in any type of crime
scene. It is now accepted throughout the world that the fingerprints science
played a major role as evidence because of the following features –
Uniqueness
The fingerprint patterns present on the first phalange of fingertips are
varying from one person to another, they are different and unique.
There duplication has not been observed. They remain unchanged and maintain
the individuality of an individual throughout the
life.
Permanence
Throughout the life time of an individual fingerprint remain constant.
Fingerprint ridges appear before birth i.e. during the third, fourth month
of pregnancy and these are the last remaining feature after death of an
individual. They are the natural identity
card given to each individual.
Universal
All individuals on the earth carry this medium of identification, this makes
them universal. A criminal always use his hands to commit any crime
resulted in leaving fingermarks on the scene of crime or on any object,
which come in contact with his fingers while
committing the crime.
Inimitable
People have attempted several methods to imitate fingerprint but successful
imitation of fingerprints is not reported so far. Any experienced expert can
identify the forgery.
Classifiable
Fingerprints have different ridges characteristics and patterns which help the
experts to systematically
classify them.
Fingerprint Uniqueness in Twins
Twins are identical twins or fraternal twins, they share the same genetics but
by taking their fingerprints
you can distinguish between them.
When an expert says that two
fingerprints are identical it means that both share the same pattern and
similar ridges characteristics. These ridges characteristics are called
minutiae. Latent fingerprints are also called hidden prints. These are the
chance prints which leftover by the perpetrator by chance at the crime scene.
Latent fingerprints are developed by experts at crime scene by powder method,
chemical method or by using alternate light source.
Fingerprints are forever but
certain genetic conditions (Adermatoglyphia) and skin condition leads the loss
or distortion of the fingerprints. Persons who are associated with tactile
works, typist, clerks, individuals associated with message work, maids etc.
also loss the fine ridges characteristics.
2) Humans are the only animals
with fingerprints –
Some animals like gorillas,
chimpanzees and koalas have unique fingerprints. Koalas prints are looking
similar to humans’ fingerprints.
3) DNA fingerprinting overshadow
the fingerprint science –
Most of the crime scenes don’t
have blood and body fluids but chances of fingerprints are more as the
objects/articles had been touched by criminals during the process of crime. So
fingerprints are still the most commonly found evidence at the scene of crime.
4) System does all the work –
A big misconception is that the
computer system (AFIS-Automated Fingerprint Identification System) does all the
work but the system is automated not automatic, it’s the expert who does the
work. System or tools have been changed but analysis always requires an
experienced expert.
5) Professional analysts are
highly accurate, but not infallible –
To understand this point first
sees the difference between uniqueness of fingerprints and the exactness of
fingerprint identification. Both these things are completely different. When a
fingerprint lifted from a crime scene it is then searched in the database or
with the suspect fingerprints. It is a process of observation, analysis and
verification by the expert. Yes fingerprint are unique to every individual but
to match the prints an experienced expert is needed, poorly trained analysts
made damage to the fingerprint science.
In the year 2004, FBI arrested
Oregon lawyer Brandon Mayfield for his involvement in Madrid train bombings.
The basis of arrest was a partial fingerprint that matched with him. Later it
was found that the experts were wrong in there analysis, actually the print was
later matched with an Algerian man Daoud Ouhnane arrested by Spanish officials.
Fingerprint analysis is still an
extremely effective tool because it’s done good work than harm. The errors
occurred and brought to light- it was the science that conveyed them to light.
If you make a mistake, you deserve to be analyzed. National Institute of
Standards and Technology found in its study that the automated computerized
systems match latent fingerprints are correct more than 99 percent of the time
when matching fingerprints from two or more fingers.
6) Accuracy and consistency of
forensic latent fingerprint decisions -
Ten digit prints (for search
purpose and matching) are of higher quality and collected under controlled
conditions by ink method on prescribed form or digitally with the help of a
live scanner system from a known subject.
Latent print examination is
difficult because latent prints are often unclear, distorted, smudged, or
contains fewer ridges, found overlapping with other prints or appeared on
complex backgrounds. As said earlier that a trained and experienced expert is
needed for latent print examination because latent print with poor quality, few
ridges can give wrong result.
When a fingerprint was found and
lifted from a crime scene, it is then send to the concerned department (Finger
Print Bureau) to compare with fingerprints stored in a database and against one
or more exemplars collected from suspect/persons of interest in the case. The
latent print is then searched (from a large database) in an Automated
Fingerprint Identification System (AFIS), which is designed to work on an
algorithum and selected a list of most similar to the latent comparison. Final
decisions were made by a latent print expert. If the expert finds out the same
pattern and identified a sufficient number of minutiae in the two prints, then
the final “identical” decision is recorded into the computer system, which is
again “verified” by a second expert who may or may not be blind to the initial
expert decision.
7) The identification process of
fingerprint matching is carried out accurately and reliably?
Automated Fingerprint
Identification System is used for fingerprint examination. It gives outcomes
not just for one single person but for quite a few who have identical
fingerprint characteristics. After providing possible candidates list by
computer, it’s still the expert call to carefully examines each edge, ridge and
valley for a right match—an often hard and painstaking process.
The process for latent print examination
is known - ACE-V, (as analysis, comparison, evaluation, and verification).
Analysis – In this step the
fingerprint and its suitable area for comparison is examined with clarity of
print and other details.
Comparison – The Search print
(mostly finger print and in some system palm print) compared with the
listed/sample print.
Evaluation – In this step the
similar or dissimilar points are evaluated in both prints.
Verification – Opinion is made by
one expert and cross checked by another expert.
The process is accurate and
reliable.
8) Limitations of fingerprint
science -
There’s no assurance that the
stored data will actually contain the print an investigator is looking for.
Latent print is affected by
weather conditions. When the weather is too hot the print is drown by
perspiration, when too cold, a print mark not recorded on surrounding objects,
due to less moisture. Rain and wind also affect the print condition.
During development of print by
powder method the powder can bunch and obscure ridges.
We cannot determine when a latent
print was first left on a surface. Under the accurate conditions, prints can
survive for an indefinite period.
9) Automated Fingerprint
Identification System influenced the experts –
The system provides the ordered
list of similar matches (also give scoring rate). Experts are more interested
in one of the prints that are near the top of the list and not seriously
lookout the print lying down the list.
This is only an assumption as the
expert check and identifies all the prints in the list provided by the
identification system.
10) How many points of comparison
are needed in two identical prints to be used in a court of law?
Fingerprint experts used a
“point-counting” method that involves counting the number of similar ridge
characteristics on the prints, but there is no uniform approach about how many
points of similarity are needed. Different countries fixed different minimum
point system/similar ridge characteristics. In India there is an 8 point
system. When an expert find 8 minimum minutiae (ridge ending, ridge bifurcation
etc.) at the relative position in both comparing prints then he reach the
conclusion “it’s an identical match”. India accepted the minimum 8 point
minutia formula in All India Forensic science Conference held at Srinagar
in 1973.
Conclusion
So the bottom line is fingerprint science is reliable or accurate, Fingerprint identification is the most important and essential criminal investigation tool, and should continue to be used in criminal investigation. Fingerprint science is a leader of innovation in biometrics for the last two decades.
Note - This article was first appeared and published in a forensic magazine, "forensic science: A world of uncertain certainties, Issue 1, written by the same author.