Color test/references | Constituent detected | Color change | Merits | Demerits |
---|---|---|---|---|
Dermal nitrate test (Forensic ballistics, Chemical analysis of gunshot residues (GSR), n.d.) | Nitrates | Blue color spots | 1. Major advantage of this test is that it can be applied to all nitro groups’ compound analysis. | 1. Disadvantage is that it give false positive result in presence of tobacco, leguminous plants, fertilizers etc. |
Walker’s test/Griess test (Griess, 1858) | Nitrites | Red color spots | 1. Advantage in using this technique is that it can be helpful in detecting the nitrites in partially burnt and unburnt propellants. | 1. Disadvantage is many compounds other than nitrocellulose propellants can give positive reaction e.g. Urine, fertilizer, face powder etc. |
Modified Griess test | Nitrites | Pink color | 1. Major advantage of this technique is that it can be performed within few minutes and found to be better than dermal nitrate test. | 1. It can be applied to detect nitrites only but not for GSR. |
Harrison and Gilroy’s Test (Harrison & Gilroy, 1959) | Pb, Sb, Ba | Sb—orange ring Pb—blue color Ba—red color | 1. More successful than dermal nitrate test as it cause less false positive cases. 2. Another advantage is that it can be easily applied to detect GSR samples on hand swabs. | 1. Interference with other materials at the SOC can be obtained. |
Sodium rhodizonate test (Steinburg et al., 1984; Bartsch et al., 1996) | Pb Ba | Blue to violet (pH 7) Bright red color (pH 2.8) Red-brown (any pH) | 1. Major advantage of this color test is that it can detect lead and its form in trace level. | 1. Major disadvantage with this is it cannot be applied for Ba detection |
Lunge test (Forensic ballistics, Chemical analysis of gunshot residues (GSR), n.d.) | Nitrocellulose/nitrites | Deep blue color | 1.Major advantage is it can be performed in few minutes | 1. Major disadvantage is it can give positive reaction with other everyday used chemicals. 2. Not further applied for detecting GSR on hand swabs. |
Di-thio-oxamide (DTO) test (Forensic ballistics, Chemical analysis of gunshot residues (GSR), n.d.) | Copper, nickel, cobalt | Copper—very dark-green coloration, nickel—pink to violet color, and cobalt—brown color | 1. Advantage in using this color test is that it can be applied to detect Cu, Ni and thus helpful in the case of Cupro-nickel-jacketed bullet. 2. Utilized for determining the bullet entry and exit holes in case of fully jacketed gilding metal (Cu/Zn) and cupro-nickel (Cu/Ni) bullets. | 1. Drawback with the color test is its applicability to detect nitrites only and not for GSR. 2 Another disadvantage is in presence of blood false negative result can be obtained. |
Marshall test (Forensic ballistics, Chemical analysis of gunshot residues (GSR), n.d.) | Nitrites | Purple spots | 1.Advantage of the chemical is that it mainly performed to detect the propellant particles in range of firing estimations | 1. The test is specific for nitrites and not for GSR |
Tewari test (Forensic ballistics, Chemical analysis of gunshot residues (GSR), n.d.) | Nitrites | Yellow spot | 1. Advantage of this test is that it is mainly used for determining range of firing estimations by visualization of propellant particles. | 1.Performed specifically for nitrites and not for GSR |