FORENSIC SCIENCE
LABORATORY
Dr Ajee Kuruvilla
Forensic science
Definitions
• Application of scientific knowledge to aid in
the administration of justice
• Study and application of scientific
examination and evaluation of evidence
for legal purpose
Forensic science
Includes:
• Forensic medicine (forensic pathology & forensic
psychiatry)
• Forensic toxicology
• Forensic odontology
• Forensic anthropology
• Forensic police sciences (criminalistics,
questioned documents, trace evidence,
ballistics, criminology
• Other specialties (polygraph, fingerprinting)
Principles of Forensic science
• Law of individuality
Every object, natural or man made, has an
individuality which is not duplicated in any other
object
• Principle of exchange (Locard’s principle)
When 2 objects come in contact, there is always
exchange of material
• Law of progressive change
Everything changes with the passage of time
Principles of Forensic science
• Principle of comparison
Only the likes can be compared
• Principle of analysis
The analysis can be no better than the sample
itself
• Law of probability
• Facts do not lie
‘Facts do not lie, men can and do’
facts can also be created !
Functions of FSL
• Examine, compare & evaluate physical
evidence
• Protection of innocent
• Training of police investigators
Divisions of FSL
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Chemistry
Physics
Biology
Ballistics
Toxicology
Serology
Documents
Photography
Lie detector (Polygraph)
• Keeler polygraph, Stoelling deceptograph
• Continuously records BP, pulse,
respiration & electro dermal reaction
• Fear stimulates sympathetic nervous
system, resulting in physiological changes
• Consent of subject essential
• Leading questions asked
• Relevant & irrelevant questions asked
Lie detector (Polygraph)
• One question every 20-25 sec, polygraph
chart recorded in 3-4 minutes
• Repetition of same test to check error
• Experienced polygraph examiner can
correctly detect truth / lie in 80- 90%
• Offenders, suspects, complainants,
witnesses, & informants examined
• Useful in civil cases too
Narcoanalysis (Truth serum)
Close to unconsciousness, the subject is
• Mentally incapable of resistance to
questioning
• Incapable of inventing lies to conceal guilt
• Looses inhibition & becomes talkative
• Depresses CNS, BP, slows heart rate
• Susceptible to suggestion & reveals
repressed feelings/ memories
Narcoanalysis (Truth serum)
Drugs used:
• 0.5 mg scopalamine hydrobromide (s.c)
• Sodium amytal/ sod pentothal 2.5 to 5%
(iv)
• 0.1 gm sod seconal + 15 mg morphine
sulphate + 0.5 mg scopolamine
hydrobromide (s.c)
Hypnosis
Helps in reviving memory of cooperative
subjects
Brain fingerprinting
• Dr Lawrence A Farwel (USA)
• Electro cap
• Suspect questioned about crime along
with visuals of crime scene
• To stimulate his brain & encourage a
reaction on a computer monitor
Brain fingerprinting
• Neuro impulses (brain waves, chemical
responses) recorded
• Intensity of brain wave shoots up
whenever a question / visual stimuli
matches the info stored in brain, if guilty
• This is tracked and printed
• Brain fingerprinting said to be more
accurate than polygraph test
QUALITATIVE ASSAYS
• Thin layer chromatography
QUANTITATIVE ASSAYS
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Ultra violet spectrophotometry (UVS)
Gas chromatography (GC)
High performance liquid chromatography(HPLC)
Mass spectrophotometry (MS)
Radio-immuno assay (RIA)
Enzyme mediated immuno assay technique (EMIT)
Atomic absorption spectrophotometry (AAS)
Neutron activation analysis (NAA)
THANK YOU