The reagent used to detect presence of Vaginal Cells in on the penis of an accused in a rape case is Lugol’s Iodine

Question 69

The reagent used to detect presence of Vaginal Cells in on the penis of an accused in a rape case is

a.       Lugol's iodine

b.      Phenophthalein test.

c.       Orthotoluidine test.

d.      Benzidine. 

Answer

a. Lugol’s Iodine

Reference

P.C.Dikshit 1^st Edition Page 395

Discussion

If the accused has had a sexual intercourse with the victim, there could be vaginal cells over his penis. These vaginal cells can not be seen with the naked eye, but can be detected by chemical. These cells turn brown when exposed to the vapors of Lugol's iodine.

The skin of the penis is wiped with a filter paper moistened with salt solution and then it is exposed vapors of Lugol's iodine. It the filter paper turns brown, the accused as had sexual intercourse.

Explanation

1. Benzedine test: Stain Extract in Test Tube + few drops of 10 % Benzidine in Glacial Acetic Acid + few drops of H₂O₂ à Blue Colour indicates Positive test (Similarly the stain is moistened with Normal Saline and a blotter is pressed over the area  + Benzidine Solution + H₂O₂ à Blue Colour indicates Positive test.

2. Phenophthalein test (Kastle mayer test): Diluted Stain Extract + Reduces Alkaline Phenopthaline + few drops of H₂O₂ à Pink Colour indicates Positive test

3. Orthotoluidine test (Kohn and O’Kelly test): Equal volume of Working Solution (4% Orthotoludine in Ethyl Alcohol + Glacial Acetic Acid + Distilled Water in equal amounts ) and H₂O₂ are mixed . Then few drops of this mixture is added to the stain extract in a test tube à Blue or Green Colour indicates Positive test

Comments

The paper turns brown in colour due to the high glycogen content of vaginal cells, when present.

Tips

While we find Glycogen with Iodine in this test, there is another test where the plant equivalent of Glycogen (ie Starch) is used to find Iodine. It is done to find out whether the common salt is iodised or not