Category Archives: Forensic Serology

Seminal fluid Analysis in forensics

Seminal fluid is a complex mixture of secretions from at least four male urogenital glands.  The seminal vesicle gland contributes approximately 60% to this mixture, the prostate gland contributes approximately 30%, and the combined contribution of the epididymis and bulbourethral glands account for the remaining 10%.

Number of Spermatozoa – 50,000 to 3,50,000.

Color – Greyish Yellow / Greyish White.

Odour – seminal odour.

pH – 7.3-7.5.

Appearance – Thick and Semitransparent,

Density – 1.028.

Semen consists of the following

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Urine Analysis

INTRODUCTION

Detecting and identifying body fluids at a crime scene can provide essential information about a crime or incident and the people involved. Like other physical flood forensic experts or scientists may be asked to recognize the presence of urine in cases such as harassment, rape or murder.

Urine is a difficult bodily fluid to detect due to the sensitivity of available tests and low positive results. The nature of the fluid causes it to dilate and thin out on the surfaces of the fabric, and it makes it harder to find. Smell may be an indicator, but it will cover a whole thing and will not be local to the area with stains.

Composition of Urine

  • It is mainly composed of water with urea, organic salts, proteins, hormones and a huge range of metabolites. It generally contains about 60 parts of water and 40 parts of solid materials.
  • Urea is an organic compound that is found in higher concentrations in urine than any body fluid.
  • Creatinine is another organic compound present in high concentrations in urine.
  • Unusually it may contain sugar albumin by pigment in case of jaundice as abnormal amount of one and other of its normal component.

Visual/ Physical Examination

Following are considered as important attributes in this initial examination:

  • Color
  • Transparency
  • Turbidity
  • Odor
  • Volume
  • pH
  • Specific Gravity

SPECIFIC GRAVITY

  • Generally specific gravity is measured by Refractometer.
  • The specific gravity of urine is higher than water.
  • The specific gravity of urine is 1.06 to 1.0 whereas water specific gravity is 1.

pH

4.5 – 8.5

(It is indicator of diet.)


Examination For Urine

GEE’s Methods or Urea Nitrate Crystals Test

In This Method Colorless 4 To 6 Sided Rhombic Shape Urea Nitrate Crystals Formed If Positive After Adding A Drop Of Conc. HNO3.

DMAC TEST

The DMAC (para-dimethylaminocinnamaldehyde)test is perhaps one of the most common methods for detecting urine based on the presence of urea, producing a pink or magenta color if positive.

INDICAN TEST

Stain Treated With Resorcinol Reagent And CuBr2 Will Produced RedColour Which Show Presence Of Indican.

CREATININE TEST

In this test chromatographic paper of stain treated with 2N NaOH followed by a drop of picric acid produced Orange/Red/Brown colour if positive.

JAFFE TEST

Creatinine is another compound found in high concentrations in urine, thus a number of tests have attempted to utilise this for urine identification tests. The Jaffe test utilises picric acid which, in the presence of creatinine, forms a red compound known as creatinine picrate. The colour change is proportional to the concentration of creatinine present.

SALKOWSKI TEST

The Salkowski Test Produces A Blue Colour In The Presence Of Urine Via A Reaction Between Sodium Nitroprusside And Creatinine When Heated.

RSID (Rapid Stain Identification Series)

The immunological RSID test has also been developed for the detection of urine, based on the presence of a urinary protein known as the Tamm-Horsfall protein.

Acid phosphatase Test

Acid phosphatase testing is one of the most common tests for semen detection in forensic laboratories. 

The Acid Phosphatase test detect presence of semen by direct testing or indirect testing.

For Direct testing a drop of extract is placed onto filter/blotting paper which contains Suspected sample and in the case of Indirect testing, disputed sample with stain is pressing with dampened filter/blotting paper on to the surface to move some fluid/stain on paper. Then filter/blotting papers are tested with a chemical reagent, which changes colour from orange to purple which confirms the presence of acid phosphatase. This is due to hydrolysis of the α-napthylphosphate to produce α-napthol, which couples with a Brentamine Fast Black/Blue salt, produce purple azo dye. 

Electrophoresis Test

By @forensicfield

What is Electrophoresis Test?

Electrophoresis is being used for the separation of various enzyme system.

There are two type of electrophoretic method have been recommended for identification of blood stains;-

  • 1] Separation and identification of hemoglobin by electrophoresis, and,
  • 2] Separation and identification of serum proteins by immunoelectrophoresis.

Immunoelectrophoresis is a two‐stage process:

  • 1.} Electrophoresis is conducted, and;
  • 2.} Immunoprecipitation using antibodies against specific proteins.

Resolution is improved by staining the proteins.

The technique is widely used to identify monoclonal immunoglobulins (M‐components) in serum and urine.

It’s Uses In Forensics

It’s a Confirmatory test for blood.

Basis Of The Test

This process involves the separation of Marker Proteins that are found on the surface of red blood cells.

Indication for the Presence of Blood

Electrophoresis  can be used to isolate and compare DNA, Blood proteins and inorganic substances.

How To Perform This Test ?

For Analyzing of Proteins

Drawbacks

The disadvantages are that gels can melt during electrophoresis, the buffer can become exhausted, and different forms of genetic material may run in unpredictable forms.

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Spectrophotometry Test

By @forensicfield

What is Spectrophotometry Test?

Spectrophotometry is measuring intensity of light in a part of the spectrum as transmitted by particular substances.

Spectrophotometry Test is based on the identification of hemoglobin and its derivatives (such as; methamoglobin, carboxyhemoglobin, oxyhemoglobin.) through their specific absorption spectra.

It’s Uses In Forensics

It’s a Confirmatory test for blood.

This method was considered one of the most conclusive test for the identification of blood stains.

Basis Of The Test

Hemoglobin and its derivatives exhibit characteristic bands of absorption at specific wavelength , which can be observed by spectrophotometer.

Indication for the Presence of Blood

It produced specific absorption spectra for hemoglobin and its derivative for identification of blood.

How To Perform This Test ?

A complex system of band is present because of heme (part of hemoglobin) in the near UV and Visible region of spectrum.

Sometimes they differs from derivative to derivative of heme portion but they all have common strong absorption band  at 400-425 nm which is also known as Soret Band.

Drawbacks

  • It can not differentiate between Sample and things which produce same wavelength.
  • Low Sensitivity.

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