Paraffin Test

PARAFFIN TEST A method used for detection of gunshot residue. This test determines whether a person has discharged a gun, the Paraffin-Diphenylam Paraffin-Diphenylamine ine test. test. Different names of this test: 1. Lunge’s test 2. Diphenylamine test 3. Dermal nitrate test 4. Gonzales test- the one who improved the test 

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Dr. Gonzalo IturriosIturrios- first used paraffin for collecting gunpowder residues from discharged firearm in Cuba where the Paraffin test originated. The basis of this test is the presence of nitrates of  nitrates in the gunpowder residue. The test is done by applying warm melted paraffin wax on the hands of the alleged shooter and causes the pores of the skin to open and exude the particles of gunpowder residue. These particles are extracted by the paraffin cast (made of  paraffin wax and absorbent cotton) and will appear as blue specks, specks, when diphenylamine (DPA) reagent is added on the cast. The specks are generally located on the area of the thumb and forefingers. Time allotment for performing a paraffin cast: 72 hours (3 days) from the time of the alleged shooting incident. After the specific period, it will be impossible to extract the gunpowder nitrates. Nitrates from pores cannot be removed by ordi nary washing of the skin and stay for 72 hours. That is why it is i s important to conduct the paraffin casting within the specific period. Characteristics of positive result for nitrates from gunpowder residue: “ tailing deep blue specks”  specks” . Thus, nitrate from other sources like fertilizers, will give the same reaction of a blue color but without the “tailing”. Other substances similar to nitrate known as oxidizers will also react with the reagent in the same way.

Substance giving false positive result: 1. Fertilizer 2. Explosives 3. Tobacco 4. Urine 5. Certain cosmetics 6. Food samples 7. Cigarette 

Paraffin test is NOT conclusive evidence but just corroborative evidence which intends to support the testimony of eyewitness/es. There are instances wherein the person who actually discharged a gun still gives a negative result because of  several factors.

Factors for false negative result: 1. Type of caliber of ammunition 2. Use of gloves

3. 4. 5. 6. 7. 8.

Length of the barrel Age of the gun/ efficiency of mechanism Direction of firing Wind direction and velocity Humidity/ percentage moisture in air When 72 hours has already lapsed

Paraffin wax - is a white, translucent, tasteless, odorless solid consisting of a mixture of solid hydrocarbons of high molecular weight.

Paraffin Casting

Materials and Apparatus: Paraffin wax Bond paper Beaker or casserole

Absorbent cotton Burner Tongs

Procedure: 1. Heat the paraffin wax in a beaker/ casserole until it melts. Allows cooling for a few minutes so that it will not burn the skin. 2. Let the subject wash hands with water without using any soap or detergent. Wipe the hands of the subject with clean absorbent cotton. 3. Let the subject place his hands on a clean sheet of bond paper with the palms facing downward and the fingers closed together. Using a spoon or tong with cotton, pour the melted paraffin wax on the hands of the subject from the thumb and index fingers and the dorsal portion to the li ttle finger side of the hands. 4. Cover the hands and fingers thoroughly with paraffin wax and place a thin layer of  absorbent cotton to reinforce the wax. 5. Pour another layer of the wax until absorbent cotton has totally absorbed the wax. 6. Allow the wax to cool and solidify to form a cast before peeling them off. 7. When cooled, direct the subject to move the fingers first and slowly moving his hands out from the casts. 8. Place on the bond paper the case number, name of the subject, time and date, technician who took the cast, witnesses and label the right and l eft hand. 9. Place another bond paper on top of the paraffin casts and staple together. 10. Place the paraffin casts inside an envelope or a box for proper preservation.

PARAFFIN CASTING Data and Results Name:______________________________ Group:________

Course and Section:____________ Date:________________________

1. Were you able to make a paraffin cast?

2. Which hand did you use?

3. Was it successful? How did you fi nd the experience? Explain.

4. What is the substance used to determine the result for presence of nitrates from gunpowder residue in the paraffin cast? What is the expected result for positive?

5. What substances that gives a false positive result? How do they differ from the positive result?