Home Archive Vol 35, No.3, 2009 Original Papers Experimental Study Forensic and Criminology to Determine Firing Distance Away from the GSR Analysis of Specific Microscopic Colored with Rhodizonat of Na

Experimental Study Forensic and Criminology to Determine Firing Distance Away from the GSR Analysis of Specific Microscopic Colored with Rhodizonat of Na

Raţă H. M.

(1)Dept. Forensic Medicine, Faculty of Police, Academy of Police, "Al. I Cuza", Bucharest

Abstract: The intention of this experiment was to investigate if a connection can be made between the microscopic distribution of GSR at derm level and firing distance. So, we used 125 experimental shooting on pig case on which the firing distance was predetermined. After the shooting, took place the derm was cropped with the adjoining tissue and microscopic exam using a specific pigment with sodium rhodizonate. The results that have been obtained were compared with the results of another experiment published in specialty journals. From present data, as a result we notice that the analyses of histopathology entrance wounds tissue using this coloring is a very useful forensics and legal medicine solution in firing distance estimated.

Keywords: gunshot residue (GSR), entrance wounds, tight contact, loose contact, close range.



Determining the distance of shooting is an element of maximum importance in medico – legal expertise lesions produced by firearms and is only able to establish with certainty the circumstances of the injuries occur and how the death (suicide, homicide or accident ).

Currently determining the shooting distance is done by examining the macroscopic of skin and holes for entry and exit of the projectile or by examining the distance between holes in the case of injuries produced by firearms.

In some cases, the presence of GSR on tegument on the victim is associated with the trajectory calculated from the hole entrance and exit and the presence or absence of GSR alleged aggressor on the skin, combined analysis allow a deeper understanding of the circumstances of production of lesions produced by firearms.

Material and method

The purpose of our experiment was to determine whether you can make a strong correlation between the microscopic distribution of GSR at the skin and shooting distance. In the study we used hand-held weapons (guns) of 9 mm caliber.

We used 125 shooting of a fire, with shooting distance made on the experimental semi-pig carcasses in the shooting distance was predetermined:

-      Shooting with glued pipe and semi-glued.

-      Shooting the limits of action of GSR.

-      Beyond the level of action of GSR.

After the shooting, the tegument was cut with a safety margin of 2 – 2, 5 cm and was harvested together with adjacent subcutaneous tissue.

 For quantitative assessment of microscopic GSR we used a specific color – acid rhodizonic associated with a salt of NA in proportion of 97% - Sigma Aldrich ( 0,3 grams per 100 ml. water) dissolved in a solution of L-tartaric acid – Sigma Aldrich at a rate of 5 to 1 – five drops of rhodizonic acid at a drop of tartaric acid.

Tissues were harvested contrast to classical hematoxilina for 30 seconds, washed and fixed in paraffin [1, 2].

Colors of rhodizonat of NA allow observation of GSR as orange particles visible in optical microscopy. GSR quantitative assessment was made using a morph metric method from the number of particles, their size and their distribution at the dermo-epidermal level.

The pictures were digital and were made at a magnification of 10x. analysis software is free-to-use (ImageJ) and is provided by the National Institute of Health (USA).

The experiment was conducted in the Police Academy “A.I.Cuza” Bucharest. Because the animals have been slaughtered for other purposes, the search has not requested pre-approval of an ethics committee.

Experimental shootings were made from five preset distances:

-      Glued pipe (0 cm.)

-      Semi-glued pipe (0,5 to 5 cm distance).

-      Pipe in less than 15 cm. distance.

-      Pipe between 15 and 40 cm. distance.

-      Pipe more than 40 cm. distance.

After coloring harvested tissues, the results were interpreted qualitatively (the GSR) and quantitatively (the dispersion of GSR).


Comments of those photos: rhodizonat of Na reacts with Pb particles presents in GSR, on that color in a very brilliant orange. The color pink is the only show that this residue of Pb. If area (orange) turns to blue after treatment with diluted hydrochloric acid, then this lead (Pb) is confirmed

The results observed in experimental shooting are presented in the following tables:

Table 1 experimental study of shooting distance Rhodizonat of NA


Number of case

Continuous aspect

Discontinuous aspect

Aspect fragmented


Glued pipe


21 (84%)




Semi-glued pipe (0.5-5 cm)


20 (80%)

5 (20%)

0 (0%)


Pipe in less than 15 cm. distance.


2 (8%)




Pipe between 15 and 40 cm. distance






Pipe more than 40 cm. distance






Grafic 1: Grafic analysis of microscop distribution of gsr in cases of assessed shooting (rhodizonat of Na)

On the surface that were finding the GSR based on the distance of firing, we observed data were as fallows:

Table 2: GSR analysis – distribution area and depth


Number of case

GSR average surface

Penetration subdermic – average (µm)

Glued pipe


2.2 x 103 mm2


Semi-glued pipe  (0.5-5 cm)


0.63 x 103 mm2


Pipe in less than 15 cm. distance


0.078 x 103 mm2


Pipe between 15 and 40 cm. distance


0.001 x 103 mm2

below 6

Pipe more than 40 cm. distance


no statistical significance

Minimal, mostly below 1

In terms of penetrations skin and sub-skin different authors [3] using sophisticated laboratory techniques have established a statistical correlation between molecular weight and penetration particles.

Graphic 2: Diameter constituent particles of gsr based on the  shooting distance (in µm2)

Graphic 3: Penetration of gsr (in µm) based on the shooting distance (our study)

For the main constituents of the powder in use and generating GSR (antimony (Sb), barium (Ba) and lead (Pb)) and a remote firing of 2,5 to 5 cm. (semi-glued pipe in our research) to obtain a curve described by the regression equation:

D (shooting distance) = a + b(1)X(1) + b(2)X(2) + b(3)X(3), where X(1) = mass Sb, X(2) = mass Ba and X(3) = mass Pb.

The formula does not generate errors in the analysis of only two elements (lead is mandatory). The results have not statistical significance shooting for the pipe at a distance greater than 40 – 60 cm. but that analysis is possible.

When a weapon is used, with the projectile in the atmosphere are eliminated and GSR counterparties of flames, gases, dust particles of explosive consisting of Pb – 9 mg., Ba – 9 mg., Sb – 4 mg. and tetrasen – 0,1 mg. ( GSR structure may differ depending on the producing country and an absolute standardization is not possible) [4].

In general, GSR highlighting is done on the spot by simple methods ( study of dermal nitrate – dermal nitrate test ) both at the victim’s tegument (entrance hole) and at the hands of individuals suspected of being involving in producing events.

At present there but also tests that can be used to quickly highlight GSR and can be confirmed by SEM (scanning electronic microscopy). A test that is standardized is the diphenylamine and is successfully used in the presentation of evidence in court [6].

For histopathological analysis of the hole of entry, Na rhodizonat can detect particles of lead and barium (GSR) and can be used to observe the penetration at the sub (skin) level in shooting made with firearms having pipe below 40 cm. away from the victim’s tegument. 

Table 3:  Frequency finding gsr in our experiment comparative with a published experiment

Shooting distance/Author

Albek (%)

Us (%)

Glued and semi-glued pipe



Detectable distance (20cm<)



Non-detectable distance (20cm>)



Graphic 4: Determining the shooting distance based on the gsr finding through specific color with rhodizonat of Na – a comparative analysis of our dates with those of literature


Following experimental shooting, we observed a good correlation between the firing distance and the total particles colored by rhodizonat of Na. Albek and collaborators [5] indicates that 42% of cases analyzed the GSR can be find by coloring with the Na rhodizonat including quantitative report (in our study 40%).

In 24% of the cases, Albek mentioned firing pipe at distance with finding GSR (20% to us) and 34% Albek failed to reveal GSR (40% in our research):


From data presented it follows that histopathological analysis of tissue entry hole using color of rhodizonat of Na represents a criminology and forensic very useful in evaluating the distance of shooting – even in conditions the gun is not found to allow the firing experiments.

The test allows (in case of shooting from short distance with glued or semi-glued pipe) qualitative and quantitative assessment of the GSR and depending on their appreciation of the circumstances to produce death.



1.     Marty W., Sigrist T., Wyler D, Determination of firing distance using rhodizonate staining technique, Int J legal Med, 2002.

2.     Neri M., Turilazzi E., Riezzo I., Fineschi V., The determination of firing distance applying a microscopic quantitative method and co focal laser scanning microscopy for determination of gunshot residue particles, Int J leg med.,2007.

3.     Santos A., et al, Firing distances estimation through the analysis of the gunshot residue deposit pattern around the bullet entrance hole by inductively coupled plasma-mass spectrometry: an experimental study. Am J Forensic Med Pathol. 2007.             

4.     Bydal BA., Percussion primer mixes, Assoc Firearms Tool Mark examination

5.     Albek E., Firearm fatalities from the aspect of suicide as the origin National Turkish Forensic Medicine meeting, 1995.

6.     Walker P., Rhodacy P., Field test kit for gunshot residue detection, Sandia National labs, FBI, Albuquerque, NM, 2005



Corresponding Adress:. Raţă H. M, MD, Dept. Forensic Medicine, Faculty of Police, Academy of Police, "Al. I Cuza", Bucharest, mail:ratahoria@yahoo.com


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