Impression Analysis
Impression Analysis
• Impressions can be individualized for
forensic purposes.
• Types of impressions: fabric prints, shoe
impressions, tire impressions & tool marks
• No two things are precisely identical & that
forensic comparison involves matching
features of questioned & unidentified
specimen with known standards
Impression Analysis – Fabric Prints
• Fabric prints are sometimes encountered
by the fingerprint expert in the form of
glove impressions.
• With use, gloves become contaminated
with substances such as dirt, grease, oils
& even sweat that enable them to leave
their imprints, either latent or visible.
• They may also leave plastic impressions in
materials like putty
Impression Analysis – Fabric Prints
• Cloth gloves may have snags, tears, or
holes that make them distinctive along
with imperfections in the weave pattern or
other identifiable characteristics.
• Leather gloves may have wrinkle or
crease formations where they do not fit
properly or they may exhibit surface
cracks, tears or other imperfections or
characteristics to individualize them
Impression Analysis – Fabric Prints
• Developing glove prints requires special
care because they are typically less strong
than fingerprints & may be destroyed by
use of too much powder.
• They should first be searched with the aid
of a flashlight, laser or other light source &
then developed with sparing use of
powder.
Impression Analysis – Fabric Prints
• Rather than lifting the print, the object on
which it is found should, if possible, be
taken to the lab for direct comparison with
a suspect’s gloves.
• Comparison prints from the gloves of a
suspect are best made on glass which is
generally the most convenient even when
the original prints are on furniture.
Impression Analysis – Fabric Prints
• Clear prints may be difficult to make, but
results may be improved by breathing
slightly on the surface of the glove’s finger.
• Other types of fabric impressions may be
found at the scene of a crime under
certain circumstances such as hit & run
accident: fabric impressions from victim
may be left in dust on assault vehicle’s
bumper, grille, fender or other area.
Impression Analysis – Fabric Prints
• Whether latent, visible, or plastic, fabric
prints should be treated in the manner
recommended for glove prints.
• In photographing them, the camera should
be at right angles to the surface to avoid
distortions
• Lifting these prints may be accomplished
with sheets of lifting material like that used
for fingerprints.
Impression Analysis – Fabric Prints
• New procedure: portable electrostatic device
operating on principle similar to static charge on
comb to lift paper; used in recovering faint prints
on colored surfaces
• Fabric impressions may show sufficient class
characteristics to demonstrate a garment could
have made the print or may exhibit individual
characteristics from wear/damage so examiner
can conclude the garment did leave impression
Impression Analysis
Shoe & Tire Impressions
• Shoe prints & tire prints are left in much
the same way as fabric impressions &
other types.
• The shoe or tire becomes contaminated
with some substance such as blood, oil, or
dust & a latent or visible print is left;
alternatively, the print may be a plastic or
3-D one, pressed into mud for example
Impression Analysis
Shoe & Tire Impressions
• Latent shoe prints are searched for &
developed in much the same way as glove
& other fabric prints.
• Whenever impression is made by dust or
other powdered material, the procedure is
first to photograph it (oblique lighting
helpful) & then lift it in manner suggested
for fabric prints by using sheets of lifting
material or by electrostatic technique.
Impression Analysis
Shoe & Tire Impressions
• Comparison footprints may be made by
coating the soles with water-based ink
applied from a large ink pad; the shoes are
then stepped onto an acetate sheet or a
sheet of tracing paper.
• When the contaminating substance is
blood, it may be developed by spraying it
with luminol which results in a faintly
glowing print observed in darkness
Impression Analysis
Shoe & Tire Impressions
• When either a shoe or tire impression has
been left in some moldable substance like
clay or snow, it’s first photographed from
directly above to avoid distortion & then
cast with plaster of paris or dental stone.
• With snow imprints, a special Snow Print
Wax is used instead. Before plaster or
dental stone hardens, identifying
information is scratched into the surface
Impression Analysis
Shoe & Tire Impressions
• FBI maintains a vast file of both shoe (sole
& heel) patterns & tire-tread designs for
such identifications
• Example: O.J. Simpson’s size 12 Bruno
Magli shoes – designer footwear both
expensive and rare – left bloody shoe
prints at crime scene that matched his
shoes
Impression Analysis
Shoe & Tire Impressions
• Tire tread impressions are almost as
useful as shoe prints. There are thousands
of tread designs & every tire wears
differently or picks up debris from the road
making it unique & identifiable.
• Each tire on the vehicle can be unique as
no two tires wear the same way
Impression Analysis
Shoe & Tire Impressions
• Dimensions may not exactly match due to
stretching of imprint from motion, distortion
due to pressure, shrinkage by drying of
earth or clay or other factors.
• What is important is that there be
discovered points of comparison (various
nicks, scratches & other effects of wear)
sufficient to effect a match.
Impression Analysis
Shoe & Tire Impressions
• For presentation of the evidence at trial,
photographs of questioned & known prints
are placed side by side with characteristic
points marked & numbered rather like the
minutiae of fingerprints.
Impression Analysis - Tool Marks
• Tool mark examinations may have begun
in Europe around turn of century. They
became common in US in 1930s following
successful use of comparison microscope
for matching striations on bullets & firingpin impression parks on shell casings.
• Methodology used for firearm examination
is fundamentally the same for toolmark
comparison
Impression Analysis - Tool Marks
• Comparisons made by demonstrating tool
mark produced by a given chisel distinct
from marks produced by any other chisels.
• Basis of tool-mark comparisons is that
implements used for cutting metal or
prying apart objects develop nicks on
edges with use & produce pattern of
striations during cutting or prying process
& is distinctive for a given tool.
Impression Analysis - Tool Marks
• Comparison microscope technique similar
to bullet comparison is used. Science
involved is called “comparative
micrography”.
• Cutting tools present a special problem
since cutting blade is long in comparison
to cut region of item involved. Examiner
will want to avoid making numerous cuts in
order to find the cutting region.
Impression Analysis - Tool Marks
• One way to accomplish this is to use
chemical spot tests to identify traces of cut
material on tool’s blade.
• To make striation comparisons, tool mark
area is placed under one barrel of
comparison microscope & the cut or
scraped area of test plate is placed under
the other.
Impression Analysis - Tool Marks
• There may be some differences due to
bending of metal during cutting or
application of uneven pressure or other
factors
• Some tools may leave an indentation or
impression that is similar to a firing pin
mark on a shell case. A hammer blow
would represent this type of mark as would
indentations caused by a pair of pliers
Impression Analysis - Tool Marks
• The comparison microscope is sued to
compare outer shape of impressions as
well as surface scratches, nicks, pits or
other defects.
• This is another procedure of comparative
micrography. There may even be a
combination of marks, both striations &
indentations.
Impression Analysis - Tool Marks
• Comparative micrography techniques may
be employed in matching a piece of
broken metal or other material and the
piece it was broken from: auto accident.
• Comparison micrography may reveal tool
impressions at a series of burglaries were
caused by the same tool, thereby linking
the crimes.
Impression Analysis - Tool Marks
• Once tool marks are discovered, they
must be protected until they can be
photographed & their locations indicated
on the crime-scene sketch.
• Two photos are required: one showing the
mark in its context, the other a close-up
photograph to reveal the minute details.
Impression Analysis - Tool Marks
• When warranted & practical, structure
bearing tool mark is removed. Otherwise,
a cast or mold may be made with
plasticine or modeling clay.
• In no event should the investigator place a
tool against a tool mark for size
evaluations as it may lead to accidental
destruction of evidence.
Impression Analysis - Tool Marks
• When submitting a tool to the crime lab for
examination, actual tool should be used;
making of test impression/cuts are
functions of qualified technicians.
• Series of test marks should be made,
applying suspected implement of varying
angles & pressures to lead plate. It
increases likelihood of duplicating details
of original mark.
Impression Analysis - Tool Marks
• Comparative micrography of tool marks
was employed to trace the ladder used in
the Lindbergh kidnapping case.
• This case gave prominence to the science
of tool-mark comparisons in much the
same way that the St. Valentine’s Day
Massacre did for firearms identification.
Case Study: Lindbergh Kidnapping
• Night of March 1, 1932: 9 pm, mother
looked in on baby – he was sleeping in
crib. 50 minutes later, nurse discovered
him missing.
• Colonel Lindbergh found nothing more
than a ladder lying beneath the nursery
window.
Case Study: Lindbergh Kidnapping
• Clues police found: ladder homemade built
in three sections for easy carrying. Upper
rung broken due to kidnapper’s weight.
• On upstairs window sill was envelope with
ransom note, no fingerprints found.
• Profile of kidnapper emerging. Ransom
note indicated a man of poor education,
almost certainly of German origin.
Case Study: Lindbergh Kidnapping
• Soon several lines of inquiry pointed to the
Bronx.
• Friend & public school principal, John F.
Condon offered reward in newspaper and
received unexpected reply.
• Condon placed an ad as requested by the
kidnapper, signing himself “Jafsie” from
the pronunciation of his initials.
Case Study: Lindbergh Kidnapping
• Jafsie received phone call arranging
meeting
• Exchange of money box for note claiming
baby being held off Martha’s Vineyard on
a boat named Nelly. Lindbergh flew there
& searched for two days.
• May 12th, decomposing body of a child
was found in woods near Lindbergh home.
Case Study: Lindbergh Kidnapping
• It was the Lindbergh baby which reported
died from head injury possibly suffered in
kidnapper’s fall from ladder.
• Forensic review many years later revealed
no skull fracture or brain injury but baby
was probably smothered at time of
kidnapping to keep him from crying &
alerting family or nurse in nearby rooms.
Case Study: Lindbergh Kidnapping
• Although Lindbergh refused to allow
money to be marked, police had secretly
recorded serial numbers & banks were
alerted to look for the bills.
• In 1933 US abandoned gold standard &
required people to turn in old bills before
May 1st. Not long before deadline, a man
signing himself as J.J. Faulkner redeemed
$2,990 of ransom money.
Case Study: Lindbergh Kidnapping
• He went to the Federal Reserve Bank in
Manhattan. Bank was too busy to recall
what the man looked like.
• A Bronx service station attendant wrote
down license plate of 1930 Dodge sedan
on back of ten-dollar gold certificate. 3
days later, bank teller recognized it as one
of ransom bills with plate number on back
Case Study: Lindbergh Kidnapping
• It was registered to Richard Hauptmann.
Police infiltrated neighborhood and worked
through the night to gather information on
Hauptmann to make decision to maintain
surveillance or arrest him.
• September 19, 1934 he was arrested for
fear he may escape. He had ransom
money in his pocket.
Case Study: Lindbergh Kidnapping
• Money was found in his garage.
• Handwriting samples from suspect were
matched to writing on ransom notes.
• It was confirmed many times over by
handwriting experts & is still used in
training examiners of questioned
documents
• The ladder finished off the rest of evidence
needed
Case Study: Lindbergh Kidnapping
• On February 13, Hauptmann was
convicted & sentenced to die in electric
chair. His petition for clemency was
rejected & execution was set for January
17th. Various postponements extended it
to April 3rd where he was pronounced
dead at 8:47 p.m. He protested his
innocence to the end even though the
governor promised him he could save his
life by telling the truth.