Certain compounds leave dark or reddish-brown stains, particularly on clothing, that closely mimic both new and old blood stains. The primary responsibility of a forensic serologist/biologist is to provide detailed answers to questions pertaining to blood analysis. Typically, the major questions that need to be addressed are:
- Is there a bloodstain?
- Also, what kind of stain is it?
A scientist must respond to such a question following a forensic inquiry. Therefore, research is done to find and identify stains that mimic blood stains.
A UV-visible spectrophotometer is a comprehensive tool for analysing a wide range of chemical compounds, pharmaceuticals, and dyes. The method is simple and straightforward for routine quality control analysis. The major advantage of UV is that it requires few solvents and little sample preparation.
The stain which resembles blood stains are:
1.) Rust stains
2.) Vegetable and Fruit Stains, Stains of Pan, Gutakha, and, Tobacco
3.) Mineral stains
4.) Synthetic dye Stain
5.) Other Stains
Rust stains on on iron weapons like sword, axe, and spade sometimes resemble dried blood stains. Similar to how iron mould or rust stains on linen might mimic ancient dried blood stains, these stains do not harden the fabric. They have a reddish-brown colour and are soluble in diluted hydrochloric acid but insoluble in water. If necessary, the stain may be oxidised with a drop of nitric acid before being subjected to the standard tests for iron, such as the potassium ferrocyanide and potassium sulphocyanide tests.
If the stain is caused by iron oxide, adding glacial acetic acid to it and then adding a drop of tannic acid solution causes it to become blue or bluish-purple.
Stains of Vegetable Origin:
Certain fruits like mulberry, currants, mangosteens, gooseberries and jambuls (Eugenia jambolana) etc. and Vegetable- like Beet, Tomato, etc. produce stains which looks like blood stain.
They are changed to a greenish-yellow colour on the addition of ammonia and are bleached by chlorine water, which has practically no effect on blood. Knives which are used to cut acid fruits not unfrequently present stains having a strong resemblance to blood stains. These stains are due to the formation of citrate and malate of iron, are soluble in water, and give rise to Prussian blue if a drop of hydrochloric acid and potassium ferrocyanide solution be added. They do not show red blood corpuscles under the microscope, but present vegetable cells and detritus.
Additionally, tobacco, henna, catechu, pan juice (with lime and catechu), and the barks, leaves, and fruits of select trees, such as babool (Acacia Arabica) and gab, all result in reddish stains (wild mangosteen or Diospyros Embryopteris). The majority of them are native to India and contain tannin, which, when combined with a drop of ferric chloride solution, can darken the stain. Diluted mineral acids will intensify the original colour, ammonia will turn it green, crimson, or bluish-black, and chlorine water will bleach it. An alkali restores the colour of a stain left by pan juice whereas an acid removes it. There are no visible absorption bands on the spectroscope.
Some red colouring agents, such as cochineal, lac dye, alkanet root, madder red, munjeet and red hibiscus petals, produce spectra that resemble blood, but their absorption band positions are different from those of haemoglobin and its derivatives, and they are not affected by reducing agents or other reagents in the same way that haemoglobin changes into oxyhemoglobin, haemochrogram,etc. The solutions of these colouring agents also exhibit well-defined changes in the tone and depth of their colour, as well as the location of their absorption bands, when exposed to alum, boric acid, dilute ammonia, sulphur dioxide solution, or chlorine water. If the colouring substance is blood, these alterations never take place.
They generally contain oxides of Iron, Red lead. The solution may be examined for iron after hydrochloric acid has been used to dissolve it.
Artificial Dye Stains:
These stains frequently mimic ancient blood stains, but by treating them with powerful acids and alkalis, they may be clearly distinguished. For instance, nitric acid turns them yellow, and in most situations, a strong alkali solution may make them red again. No such reaction takes place in the case of blood stains.
Spots of grease, Boot polishes, resin, tar, and pitch, particularly on dark fabrics, may imitate quite old blood stains, but their solubility in alcohol, ether, chloroform, turpentine, or xylol distinguishes them. When a clean white filter paper is pressed with a hot iron on any of these stains, the paper absorbs the substance and is then tainted.
Reddish-brown faecal stains can occasionally be mistaken for old blood stains. The benzidine test may also produce a positive result due to the presence of undigested fish or meat fibres. An analysis under a microscope, on the other hand, will disclose the undigested food particles and answer the query.
1.) Dr. C.K. Parikh’s, text book of Medical Jurisprudence and Toxicology, 1990, Vth edition, CBS publisher and distributors page 620.
2.) K.S.Narayan Reddy: The Essentials of Forensic Medicine and Toxicology, twenty-third edition 2004 K Suguna Devi page 371-375
3.) Kulkarni, Ulka & Gosavi, N & Bendbhar, R & Kamat, C & Kulkarni, Krishna. (2014). DETECTION AND IDENTIFICATION OF STAINS WHICH RESEMBLES BLOOD STAIN.
4.) N.R. Gosavi et al.: Identification and Confirmation of Banana Stains from Blood Stains on Suspected Cloths, National Conference in Forensic Science 2012 Mumbai.
5.) Directorate of Forensic Science, Ministry of Home Affairs Government of India New Delhi, Laboratory Procedure Manual, Forensic Biology, 2005.
6.) Spectroscopy of organic compounds by P.S Kalsi, (fifth Edition).
7.) Parveen Kumar Janjua,et.al., An Interdisciplinary Approach to Forensic Science., Selective & Scientific Books New Delhi-110001, Ist Ed. 2005.
8.) Instrumental Methods of Chemical Analysis – Gurdeep Chatwal, (fifth Edition),
9.) Cullford B.J., (1971), The examination and typing of the blood stains in the crime laboratory, U.S. govt. printing office, Washington D.C., page 62 – 66.
10.) B.R. Sharma, Scientific Criminal Investigation Universal Law Publishing Comp., 2006, page 234.