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Archive February 2020

Forensic Serology and Biology

The forensic biology and serology is one of the crucial discipline in the field of forensic sciences. Generally, the forensic serology deals with the analysis of blood, serum, saliva, semen, hair
and other bodily fluids to establish the relationship of the perpetrator to the crime scene. The major concern of forensic serologists to collect the biological evidence present at the crime scene in an adequate way preventing them from contamination.

Blood is one of the crucial evidences and can be commonly found at the crime scene like murder, vehicular accidents, sexual assaults etc. The forensic serologists must answer the following questions at the time of examining blood, blood stain or smears:

1) Is it blood or not?

2) Is it human blood or originate from any other species?

3) If it’s human blood then how closely it can be related to the particular individual?

The preliminary step to examine whether it’s a blood or not, various colour tests are carried out by specialised forensic at the crime scene.

a) Phenolphthalein Test (Kastle – Meyer Colour Test)

The phenolphthalein test is based on the haemoglobin pigment present in blood which possess peroxidase like activity. The phenolphthalein reagent and hydrogen peroxidase mixture are applied on the bloodstain, thus causes the formation of deep pink colour. The change in colour indicates the presence of blood.

b) Luminol Test

The luminol test is the most sensitive test to detect bloodstains. The bloodstain shows fluorescence instead of producing colour. The luminol reagent is sprayed on the suspected areas, the emission of light can be viewed and thus bloodstain will produce a faint blue glow.

The confirmatory test is performed in the laboratories to determine whether it’s a human blood or not. One of the confirmatory test for origin of species is precipitin test carried out on bloodstain. The precipitin test involves the reaction of antiserum with the corresponding antigen. Another version of precipitin test is the Gel Diffusion method. The extracted bloodstain antigen and human antiserum is placed at different holes opposite to each other. The line of precipitate forms when antigen and antiserum meet, thus confirming the presence of human blood. The precipitin test gives best result even the blood stain is 10-15 years older.

                                                                                – Ravshish Kaur Kohli

                                                               (M.Sc. -Forensic Science), Amity University

Crime Scene Investigation

A crime scene is place where an offence has been committed and the investigators carefully examine or search the area in order to find probative evidence. The purpose of crime scene investigation is to establish the possible link suspect, victim, witnesses in relation to criminal event.

In the majority of cases such as homicidal, suicidal and accidental, the crime scene investigators as well as law enforcement officers play a significant role in determining proper collection as well as preservation of physical evidence which might be accidently left by the criminal. Proper documentation and photography of a crime scene should be done by specialised and well-trained personnel that could help them to reconstruct the crime scene.

A well-trained crime scene investigator (Investigating Officer) must following basic steps in order to perform proper investigation to maintain the chain of custody:

1. MedicalAssistance to the victim if there is even a remote chance of life.

2. Securingthe crime scene by barricading using barricading tape, rope or cones etc. to protect the entry of unauthorized persons like on lookers, family members, witness etc.

3. Documentationof the crime Scene

a. Photography/Videography (Over view, Mid-range and close up photography)

b. Note Taking (Complete description of the crime scene)

c. Sketching of the Crime Scene (Rough and Final Sketch)

4. Searching of the evidences

a. Strip or line search method

b. Grid Search Method

c. Spiral Search pattern

d. Wheel or Ray search pattern

e. Quadrant or Zone Search pattern

5. Collection of Physical Evidences (Following evidences should be sent to Forensic Laboratory):

a. Victim’s Clothing

b. Fingernail Scapings

c. Hairs (head or pubic hairs)

d. Gun/Bullets recovered from the crime scene or victim’s body

e. Hand Swabs from Shooting victim (for gunshot residue analysis)

f. Semen/Vaginal/Anal/oral Swabs in case of sex related crimes for DNA Profiling

g. Blood/Viscera Samples in case of poising cases

h. Debris collection in case of arson/fire cases

6. Preservation of evidence by-

a. EDTA for blood samples

b. Air dry method

c. NaCl Solution for preserving viscera

7. Packaging of Evidences should be done using

a. Unbreakable plastic pill bottles with pressure lids (hair, glass fibers)

b. Manila envelops

c. Screw cap glass vials

d. EDTA tubes for fresh blood

e. Sealable plastic bags

f. Druggist Fold

g. Paper bags

h. FTA card for collecting DNA sample

8. Naming and Tagging of evidence (complete description of the evidence)

a. Nature of evidence

b. Name of the investigating officer

c. Person collected the evidence

d. Initials of the investigating officers

9. Forwarding Letter in order to send the evidence to the Forensic Science Laboratory.

10. Releasing the Crime Scene for general Public or Family members.