Is paraffin test a reliable test for detecting gunpowder residues?
Scientific experts concur in the view that the paraffin test has proved extremely unreliable in use. It can only establish the presence or absence of nitrates or nitrites on the hand; still, the test alone cannot determine whether the source of the nitrates or nitrites was the discharge of a firearm.
What is the basis of the paraffin test in the gunpowder residue test?
The test was performed by covering a suspect’s hand with a layer of paraffin, which, after cooling, could be broken off and the paraffin treated with an acid solution of diphenylamine, a reagent used to detect the presence of nitrates or nitrites. A positive result would then be read as blue flecks on the wax.
Can Gunpowder be detected?
New Patented Sensor Technology can accurately detect gunpowder that is found in gunpowder bombs, and modern shotguns, handguns and rifles.
What can cause a false positive on a gunshot residue test?
Samples collected from occupations or simulations thereof include welding, pyrotechnics, key cutting, mechanics, and paper products all of which produced significant false positive results for gunshot residue.
Why paraffin test is important?
A forensic test to indicate whether a person has recently fired a gun, in which the person’s hand is coated in hot paraffin wax which cools and sets and is peeled off and tested for the presence of residue from the gun.
Why is paraffin test not reliable?
proved extremely unreliable in use. The only thing that it can deliberately establish is the presence or absence of nitrates or nitrites on the hand. It cannot be established from this test alone that the source of the nitrates or nitrites was the discharge of a firearm.
What are the chemical test for gunpowder residues?
An organic reagent, diphenylamine, in a concentrated solution of sulfuric acid, is added to the paraffin glove drop by drop. A positive reaction indicating the presence of gunpowder residues is indicated by the appearance of dark blue pin-point specks on the inner surface of the cast.
What is true about the presence of gunpowder residue on a person?
The presence of gunshot residue on the hands of an individual indicates that the person recently discharged a firearm, handled a firearm or an object with gunshot residue on its surface, or was in close proximity to a firearm when it was discharged.
What is the principle behind paraffin test?
Are paraffin tests reliable?
How is gunshot residue detected?
Gunshot residue (GSR) analysis is a standard method to determine if a firearm has been used. Often the primer particles containing lead (Pb), barium (Ba) and antimony (Sb) are detected and analyzed using EDS in a scanning electron microscope. …
What is a paraffin test?
noun. A forensic test to indicate whether a person has recently fired a gun, in which the person’s hand is coated in hot paraffin wax which cools and sets and is peeled off and tested for the presence of residue from the gun.
What kind of test is the paraffin test?
The test has also been referred to as the dermal nitrate test, the diphenylamine test, and the Gonzales test.115,116. The test is conducted by applying melted paraffin wax to the back of a suspect’s hands. With a brush, the back of the hand is coated with paraffin wax which on cooling solidifies and can be peeled off the hand.
What are dark blue spots on a paraffin test?
The reaction sequence is as shown in Figure 16.1.117 The detection of dark blue spots was considered as indicative of the presence of nitrates and/or nitrates from FDR.
How are nitrates and nitrites detected in paraffin wax?
The detection of nitrates and nitrites present in FDR using a color reaction with diphenylamine in sulfuric acid was first applied to firearms related examinations about 1911, and in 1914 Doctor Iturrioz used paraffin wax as a lifting medium for propellant residue on clothing prior to treatment with HNO3 Diphenylamine (colorless)
Where can you find the particles of gunpowder?
These particles are formed during the discharge of a firearm, and can often be found on the hands of a shooter within a given period after the event. The analysis of GSR in forensic laboratories has typically been achieved by scanning electron microscopy with energy dispersive X-ray spectroscopy.