Transcript Case Profile

Lesson 2
Fingerprints
Say there’s been a robbery at
a house. Police arrive the
scene. What will be the first
thing the police search for?
Why?
One of the reasons：
Fingerprint is unique. If the thief has
left a fingerprint, that could lead to a
quick arrest!
Activity 2.1
How much do you know about fingerprints?
Complete Worksheet 2.1 to check your
understanding.
Classification
1.
Arches


Ridges enter on one
side and exit on the
other side.
Approximately 6% of
people exhibit this
pattern.
2.
Loops


Ridges enter on one
side and exit on the
SAME side.
Approximately 60%
of people exhibit this
pattern.
3.
Whorls


Consists of circles
and spirals.
Approximately 34%
of people exhibit this
pattern.
Types of fingerprint evidence

Patent prints
 Visible
prints are made on a surface when the
ridges of fingers come into contact with a
colored material such as blood, paint, grease
or ink.
Types of fingerprint evidence

Latent prints
 Invisible
prints deposited on hard and nonabsorbent surfaces are usually developed by
the application of a powder, whereas prints on
porous surfaces generally require treatment
with a chemical.
 Examples of hard and non-absorbent
surfaces are glass, mirror, tile, etc.
Types of fingerprint evidence

Latent prints (Cont’d)
 Examples
of porous surfaces are paper,
cardboards.
 Examiners use various chemical methods to
visualise latent prints such as iodine fuming.
 Super Glue fuming develops latent prints by
reacting with body oil residue found in
fingerprint.
Types of fingerprint evidence

Physical prints
 Physical
prints are ridge impressions left on a
soft material, such as wax, soap and dust.
Activity 2.2: Practice the identification
skills
Fork
Double Fork
Triple Fork
Fingerprint ridge details
Delta
Dot
Bridge
Hook
Eye
Short Ridge
Ending Ridge
Activity 2.2: Practice the identification
skills
e.g. fork
Locate and label the ridge details
dot
fork
ending ridge
hook
eye
ending ridge
double hook
bridge
Activity 2.3 Making a fingerprint
(Part 1)
Part 1
1.
2.
3.
4.
5.
Direct fingerprinting (a known
fingerprint made from an individual)
Rub a 2B pencil over a white paper until it is
covered with graphite.
Rub your index finger against your nose or
forehead and place the finger on the center of a
microscope slide.
Press and roll your index finger firmly on the
graphite pad and then press the finger on the
worksheet thoroughly.
Take a transparent adhesive tape and press it onto
the fingerprint.
Repeat step 2 to 4 for another index finger.
Activity 2.3 Making a fingerprint
(Part 2)
Part 2
6.
7.
8.
Latent Fingerprinting (Fingerprinting
dusts makes latent prints visible)
Use a handkerchief to wipe a microscope slide free
of any stray fingerprints. Handle the slide only by
the edges.
Rub your index finger against your nose or
forehead and place the finger on the center of the
microscope slide.
Sprinkle the iron powder onto the edge of the print.
Activity 2.3 Making a fingerprint
(Part 2)
9.
10.
11.
12.
13.
Lightly shake the slide to apply a thin coating of
iron powder onto the latent print.
As the print becomes visible, you should shake the
slide lightly until there is no excess iron powder on
the slide.
To lift the fingerprint from the slide, you should
position the untouched portion of the tape above the
imaged fingerprint and smooth the tape over the
developed print.
Place the fingerprint on the worksheet.
Repeat step 7 to 13 for the rest of your fingers.
Activity 2.3 Making a fingerprint
(Part 3)
Part 3
1.
2.
3.
Statistics
Identify the pattern of each of your fingerprint.
Write down the name of pattern under each
fingerprint.
Count the numbers of each pattern.
Activity 2.3 Making a fingerprint
(Part 4)
Part 4



Identify the ridgeline details
Choose the fingerprint with best resolution among
all your fingerprints.
Examine the fingerprint with a magnifying glass.
Use Table 1 of Worksheet 2.2 to help identify
separate fingerprint ridgeline details. List out the
names of ridgeline details on the worksheet. Count
the frequency of each ridgeline detail.
Activity 2.3 Group discussions
1.
2.
Count the number of patterns of all
fingerprints among your group members.
What is population percentage of each
pattern? Show your calculations.
Which pattern is most common among
your group members?
Activity 2.3 Group discussions
3.
Which colour is the most popular color for
fingerprint powder? Why?
Answer:
Black is the most popular colour because it
creates the most contrast on a white card,
commonly used for filing and recording
fingerprints. This provides a uniform medium
for the comparison of black ridges of the
questioned print to the black inked ridges of
the known print.
The steps in analysing and comparing
fingerprints
Five steps in analysing and comparing fingerprints.
Step 1: Identify the general pattern of the central area of
the fingerprint.
Step 2: Match fingerprint ridgeline details.
Step 3: Compare the unknown print and the known print,
point by point, feature by feature, to see if they
match.
Step 4: Evaluate whether the unknown print matches the
known print or not.
Step 5: A second examiner verifies the results.
Steps in analysing and
comparing fingerprints
How many points of similarity between the
prints are required to match two
fingerprints?
Note:
After calculating the probability, at least 13
points of similarity between the prints are
required to identify a match between two
fingerprints.
Automated Fingerprint Identification
Systems (AFIS)
1.
2.
3.
Capturing, storing, searching, and retrieving
fingerprints via computer is now a standard
practice among police agencies and forensic
science laboratories.
Automated Fingerprint Identification Systems
(AFIS) are computerised databases of digitised
fingerprints that are searchable through
software.
An AFIS can store millions of prints which can
be searched in a matter of minutes by a single
operator.
Activity 2.4: Case study

Read the case profile.

Follow the five steps in analysing and
comparing fingerprints.

Write a report to conclude your findings.
Activity 2.4 Read the case profile
A suspect was arrested in a burglary case. When the
suspect was fingerprinted, the desk sergeant noticed
something very unusual – his fingerprints somehow had
been altered. The suspect admitted that he had peeled
off the skin from one of his thumbs and transplanted it
onto another thumb. The suspect even claimed that “I
have new thumbprints. I am a clean person.”
Furthermore, the police have recovered an excellent
latent thumbprint from an unsolved burglary case 3 years
ago. There are some indications that these 2 cases may
be related.
Activity 2.4 Your role…



The recovered print and the suspect’s new
thumbprints are provided for your analysis.
Can a match be made between the direct
thumbprints from the suspect and the latent
thumbprint found at the crime scene?
Imagine you were a fingerprint examiner and
you need to evaluate the presented evidence,
reach conclusions and provide findings in a
report to the law enforcement authorities and
the court.
Activity 2.4 Fingerprints to be
examined…
Known left
thumbprint
from suspect
Known right
thumbprint
from suspect
Recovered
print from
burglary scene
Activity 2.4 Before you start…
Discuss with your group members:
 In order to analyse and compare
fingerprints, what will be the next steps?
 If necessary, you may use a mind map or
concept map to show your answers.
Activity 2.4: At the end…
In you report, you should
 identify
whether there is a match between the latent
print and the direct prints. Circle and label the area(s)
on the direct thumbprint and recovered latent print
correspondingly.
 identify
which part of the thumbprint was altered.
Circle the area(s) on the direct thumbprint and
recovered latent print correspondingly.
Suggested Answers
Known left thumbprint from suspect
Recovered print from robbery store
Suggested Answers
Known left thumbprint from suspect
Known right thumbprint from suspect
Activity 2.4 Follow-up group
discussions
1)
“The suspect admitted that he had
peeled off the skin from his left thumb
fingertip and transplanted them onto his
right thumb.”
Explain whether the new fingerprint would
last forever.
b. Is the suspect identified? If you were a
member of the jury, would you believe the
“evidence”?
a.
2)
Suggest how one would not leave his/her
fingerprints. Justify the possibility.
3)
Are lip prints or toe prints unique like
fingerprints? Explain briefly.
4)
Comment the statement “A fingerprint
classification system can unequivocally
identify an individual. ”