A fingerprint is an impression normally made by ink or contaminants
transferred from the peaks of friction skin ridges to a relatively smooth
surface such as a fingerprint card. These ridges are sometimes known as "dermal
ridges" or "dermal papillae". The term fingerprint normally refers to
impressions transferred from the pad on the last joint of fingers and thumbs,
though fingerprint cards also typically record portions of lower joint areas of
the fingers (which are also used to effect identifications). Friction skin
ridges are not unique to humans, however, and some species of primate also have
friction skin ridges on "fingers" and paws in configurations sometimes similar
to human friction ridge skin. Old world monkeys also have friction ridge skin on
their tails, possibly associated with use of their tails for gripping during
climbing. Friction skin ridges on humans are commonly believed to provide
traction for grasping objects. In the over 100 years that fingerprints have been
examined and compared, no two areas of friction ridge skin on any two fingers or
palms (including between identical twins) have been found to have the same
friction ridge characteristics.
The tip of a finger showing the
fingerprint.
The same fingerprint as it would be detected on a
surface.
Fingerprint Identification
Fingerprint Identification (sometimes referred to as Dactyloscopy) is
the process of comparing questioned and known friction skin ridge impressions
from fingers, palms, and toes to determine if the impressions are from the same
finger (or palm, toe, etc.). The flexibility of friction ridge skin means that
no two finger or palm prints are ever exactly alike (never identical in every
detail), even two impressions recorded immediately after each other. Fingerprint
identification (also referred to individualization) occurs when an expert (or an
expert computer system operating under threshold scoring rules) determines that
two friction ridge impressions originated from the same finger or palm (or toe,
sole) to the exclusion of all others.
Latent Prints
Although the word latent means hidden or invisible, in modern usage for forensic science
the term latent prints means any chance or accidental impression left by
friction ridge skin on a surface, regardless of whether it is visible or
invisible at the time of deposition. Electronic, chemical and physical
processing techniques permit visualization of invisible latent print residue
whether it is from natural secretions of the eccrine
glands present on friction ridge skin (which produce palmar sweat, but no
oils), or whether the impression is in a contaminate such as oil, blood, paint,
ink, etc.
Patent Prints
These are prints which are obvious to the human eye and are caused by a
transfer of foreign material on the finger, onto a surface. Because they are
already visible they need no enhancement, and are photographed instead of being
lifted. Where possible, the item containing the print is taken away and looked
at by forensic scientists.
Plastic Prints
A plastic print is a friction ridge impression from a finger or palm (or
toe/foot) deposited in a material that retains the shape of the ridge detail.
Commonly encountered examples are melted candle wax, putty removed from the
perimeter of window panes and thick grease deposits on car parts. Such prints
are already visible and need no enhancement, but investigators must not overlook
the potential that invisible latent prints deposited by accomplices may also be
on such surfaces. After photographically recording such prints, attempts should
be made to visualize other non-plastic impressions deposited in natural
finger/palm secretions (eccrine gland secretions) or contaminates.
Classifying fingerprints
There are three basic fingerprint patterns: Arch, Loop and Whorl. There are
also more complex classification systems that further break down patterns to
plain arches or tented arches. Loops may be radial or ulnar. Whorls also have
sub-group classifications including plain whorls, accidental whorls, double loop
whorls, and central pocket loop whorls.
Timeline
There is no clear date at which fingerprinting was first used in prehistoric
times. However, significant modern dates documenting the use of fingerprints for
positive identification are as follows.
Fingerprints collected at a crime scene, or on items of evidence from a
crime, can be used in forensic science
to identify suspects, victims and other persons who touched a surface.
Fingerprint identification emerged as an important system within police agencies
in the late 19th century,
when it replaced anthropometric measurements as a more reliable method for
identifying persons having a prior record, often under an alias name, in a
criminal record repository.
The science of fingerprint identification stands out among all other forensic
sciences for many reasons, including the following:
- Has served all governments worldwide during the past 100 years to provide
accurate identification of criminals. No two fingerprints have ever been found
alike in many billions of human and automated computer comparisons.
Fingerprints are the very basis for criminal history foundation at every
police agency.
- Established the first professional certification program for forensic
scientists, the IAI's Certified Latent Print Examiner program (in 1977),
issuing certification to those meeting stringent criteria and revoking
certification for serious errors such as erroneous identifications.
- Remains the most commonly used forensic evidence worldwide - in most
jurisdictions fingerprint examination cases match or outnumber all other
forensic examination casework combined.
- Continues to expand as the premier method for identifying persons, with
tens of thousands of persons added to fingerprint repositories daily in
America alone - far outdistancing similar databases in growth.
- Outperforms DNA and all other human identification systems to identify
more murderers, rapists and other serious offenders (fingerprints solve ten
times more unknown suspect cases than DNA in most jurisdictions).
Although some reporters and exposè authors claim that fingerprints have long
enjoyed a mystique of infallibility, the opposite is true. Fingerprint
identification was the first forensic discipline (in 1977) to formally institute
a professional certification program for individual experts, including a
procedure for decertifying those making errors. Other forensic disciplines later
followed suit in establishing certification programs whereby certification could
be revoked for error.
Fingerprint identification effects far more positive identifications of
persons worldwide daily than any other human identification procedure. The
American federal government alone effects positive identification of over 70,000
persons most days, including US Visit (Department of
Homeland Security) and Federal Bureau of Investigation fingerprint activities. A large
percentage of the identifications (approximately 92% of US Visit
identifications) are effected in a lights-out (no human involved) computer
identification process with 100% accuracy based on only two fingerprints.
As in any field of human endeavor, errors in fingerprint identifications can
and do occur. Such errors in fingerprint identification are so rare that when
they occur, they normally make headlines worldwide. One of the most famous
fingerprint identification mistakes was made by the FBI Laboratory in 2004.
Although the FBI Laboratory had previously made about one latent fingerprint
identification error each eleven years, the 2004 error was the first instance in
the 84 years of the FBI Laboratory's operation when an error was not discovered
and corrected before it caused an innocent person to be jailed.
Below are several noteworthy examples of fingerprint errors:
Brandon Mayfield
A case of misidentifying a print: Brandon
Mayfield is an Oregon lawyer who was
identified as a participant in the Madrid bombing based on a fingerprint match by the FBI. The FBI
Latent Print Unit ran the print collected in Madrid and reported a match against
one of 20 fingerprint candidates returned in a search response from their
Integrated Automated Fingerprint Identification (IAFIS) system. The FBI initially called the match "100 percent
positive" and an "absolutely incontrovertible match". The Spanish National Police examiners concluded the prints
did not match Mayfield and they eventually identified another man who matched
the prints. The FBI later acknowledged they were in error and he was released
from custody. In January of 2006, a U. S. Justice Department report was released which faulted the FBI for
sloppy work but exonerated them of more serious allegations.
Shirley McKie
A case of misidentifying a print: Shirley McKie
was a policewoman in 1997 when she was
accused of leaving her thumb print inside a house in Kilmarnock, Scotland where
Marion Ross had been murdered. Although PC McKie denied
having been inside the house, she was arrested in a dawn raid the following year
and charged with perjury. The only
evidence was the thumb print allegedly found at the murder scene. Two American
experts testified on her behalf at her trial in May 1999 and she was found
not guilty. The Scottish Criminal Record Office (SCRO) never admitted a mistake.
On February 7, 2006, McKie was awarded
£750,000 in
compensation from the Scottish
Executive and the SCRO.[1]
Controversy continues to surround the McKie case with calls for the resignations
of Scottish ministers and for either a public or a judicial inquiry into the
matter.[2]
Stephan Cowans
A case of misidentifying a print: Stephan Cowans was convicted of attempted
murder in 1997 after he was accused of the shooting of a police officer while
fleeing a robbery in Roxbury,
Massachusetts. He was implicated in the crime by the testimony of two
witnesses, one of which was the victim. The other evidence was a fingerprint on
a glass mug that the assailant drank water from, and experts testified that the
fingerprint belonged to him. He was found guilty and sent to prison with a
sentence of 35 years. While in prison he earned money cleaning up biohazards to
accrue enough money to have the evidence tested for DNA. The DNA did not
match his, he had already served six years in prison before he was released.
William West
A story that some regard as apocryphal circulates about events occurring in
the early 20th century
when a man was spotted in the incoming prisoner line at the U.S. Penitentiary in
Leavenworth,
Kansas by a guard who recognized him and thought he was already in the
prison population. Upon examination, the incoming prisoner claimed to be named
Will West, while the existing prisoner was named
William West. According to their Bertillon
measurements, they were essentially indistinguishable. Only their fingerprints
could readily identify them, and the Bertillon Method was discredited. There is
evidence that men named Will and William West were both imprisoned in the
Federal Penitentiary in Leavenworth, Kansas, between 1903 and 1909. However, the
details of the case are suspicious, especially since they differ between
retellings, and the story did not appear in print until 1918. Today, people
familiar with the story differ on whether the story was accurate, a test of
people (possibly separated twins) who bore a striking resemblance, a test of
known twins, or complete fiction. The story of Will
West is mentioned on page 167 of Forensic Uses of
Digital Imaging by John C. Russ, with mug
shots of "the two Will Wests" on page 168.
Footprints
Friction ridge skin present on the soles of the feet and toes (plantar
surfaces) is formed with the same uniqueness as ridge detail on fingers and
palms (palmar surfaces). When recovered at crime scenes or on items of evidence,
sole and toe impressions are used in the same manner as finger and palm prints
to effect identifications. Footprint (toe and sole friction ridge skin) evidence
has been admitted in US courts since 1934 (People v. Les, 267 Michigan 648, 255
NW 407).
Footprints of infants, along with thumb or index finger prints of mothers,
are still commonly recorded in hospitals to assist in verifying the identity of
infants. Often, the only identifiable ridge detail in such impressions is from
the large toe or adjacent to the large toe, due to the difficulty of recording
such fine detail. When legible ridge detail is lacking, DNA is normally
effective (except in instances of chimaerism) for indirectly identifying infants
by confirming maternity and paternity of an infant's parents.
It is not uncommon for military records of flight personnel to include bare
foot inked impressions. Friction ridge skin protected inside flight boots tends
to survive the trauma of a plane crash (and accompanying fire) better than
fingers. Even though the U.S. Armed Forces DNA Identification Laboratory (AFDIL)
stores refrigerated DNA samples from all current active duty and reserve
personnel, almost all casualty identifications are effected using fingerprints
from military ID card records (live scan fingerprints are recorded at the time
such cards are issued). When friction ridge skin is not available from deceased
military personnel, DNA and dental records are
used to confirm identity.
US Fingerprint Databases
The FBI manages a fingerprint identification system and database called IAFIS, which currently holds the fingerprints and criminal
records of over fifty-one million criminal record subjects, and over 1.5 million
civil (non-criminal) fingerprint records. US Visit currently holds a repository
of over 50 million persons, primarily in the form of two-finger records (by
2008, US Visit is transforming to a system recording FBI-standard tenprint
records).
Source: Internet