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Ballistics- evidence at Gunpoint

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Forensics: exact science or dramatised fiction? #3


Nothing fascinates the people more than the police and the forensics team ‘proving’ that the fatal bullet was fired by the accused and nobody else and that too from nothing else except the pistol or revolver recovered from him.

This trend started during the British era in 1924 when Sydney Smith employed as a medico-legal expert by the Egyptian government, for the first time used his knowledge of ballistics to ‘identify’ the gun used to assassinate Lee Stack Pasha, Commander in Chief of the Egyptian army. Smith went on to write an interesting book called ‘Mostly Murder.’ Since then ballistics has caught the fancy and subconsciously influenced millions of people into thinking that forensics is an exact science, which it is not.

Ballistics seeks to do many, almost impossible things like how the bullet in question was fired; the weapon that fired it; and whether the empty shells recovered from the scene of crime match with the weapon.

Comparison of bullets by human eyes is fraught with errors

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As discussed in the first article of this series, the comparison applies to bullets that are fired from ‘rifled barrels’ as against smooth barrels. Muskets used until the late 19th century had smooth barrels—most of the modern shotguns also necessarily have smooth barrels. In rifled barrels, the bullet fits snugly in the barrel and moves along it after engaging helical grooves cut in the barrel that make it spin for stabilized flight. Now, barrels are made of very hard steel and bullets have usually a soft copper jacket. The soft material develops striations from the hard material of the rifling.

In the early days of firearms manufacture, rifling was cut into the barrel by a simple machine called ‘rifling lathe’, not much different from the lathes you see in your neighbourhood workshops. It was not a precision machine and as a result, it could be expected that no two riflings would be exactly the same. The situation has changed dramatically now with modern precision machines like Computer Numerical Control lathes. 

All they did was to take two bullets (one recovered from the body and another recovered from firing a ‘test bullet’ from the suspect gun into glass wool) and compare the striations made on them under a device called Comparison Microscope to see if they are similar or different. They continue to do the same 100 years later also!

That was the catch! Comparison by human eyes cannot be reliable—it is a subjective evaluation of what one perceives and hence subject to grave errors as different people could perceive the same things differently.

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Chemical analysis of the composition of bullets is equally farcical

Pure lead is very soft. Hence bullet manufacturers add elements like copper, antimony, bismuth, arsenic, tin, and silver to each batch of lead to make a lead alloy with specific metallurgical properties suitable for a bullet.  From one batch to another, the proportions in bullets of the six elements may vary slightly. The idea of comparative lead analysis is to determine the percentage of these trace elements. However, all that it can ever find out is that the bullets belong to the same batch of manufacture, nothing more.

Hundreds of thousands of bullets are made in one batch and they are bought by an equally large number of people, which makes it impossible to connect a bullet with a particular accused. Even before the National Academy of Sciences reports in 2009, the FBI had abandoned this analysis in 2006 itself.

All this exercise fails when steel bullets are used. Indian police officers and so-called forensic experts do not know that, in order to reduce costs, many companies like Norinco are now making steel core bullets by the millions.

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Also Read:

Forensics: exact science or dramatised fiction? #1

Post mortem reports – the big farce, justifying untruth

Gunshot residue (GSR) analysis, the greatest hoax of them all

Gunshot residue tests were based on the presumption that as a gun is discharged, the smoke escapes from the gun in the form of a vapour or ‘plume’ through any available openings in the weapon. Minute particles of the smoke could settle onto the hands, clothing, and surfaces in the immediate proximity of the discharged weapon, besides the insides of the gun barrel. This is loosely called GSR (gunshot residue) or FDR (firearm discharge residue). The notion harboured in the early days of forensics was that if the presence of these particles could be established by chemical analysis; it would prove that the person had fired. It never occurred to these ignorant enthusiasts that, from the point of view of the law, even if it is somehow proved that a person had fired in the recent past or that his gun had fired, it does not establish any connection of the firing with the crime in question.

For example, one who holds a licensed weapon for self-defence is not supposed to keep it under lock and key all the time. He is supposed to practice with it at the local rifle club or some other shooting range. Very many people use their shotguns for sports like trap shooting or skeet shooting. Now, most people are not very good at cleaning the guns themselves after use. At most, they would run a brush through the barrel. Some people give their guns after months to gun dealers for cleaning. Brush cleaning cannot remove all the microscopic particles deposited inside the barrel. This means that if those barrels are tested for GSR anytime, they would test positive, even as the gun had been used for legitimate purposes only. GSR tests on hands and clothes etc. are also equally misleading. Moreover, if an accused is not arrested from the spot and isolated immediately thereafter, he could wash his hands thoroughly and eliminate all GSR.

Since the particles do not adhere to the surfaces with any significant adhesive force, there is always a very strong possibility of cross-contamination. The slightest touch with any other surface can transfer them both ways—from the hands, which had them to a surface, which had not them; and also from a surface which had them on to a hand which never had them.

From a legal perspective, GSR tests (usually for nitrates in the propellant) are useless because there is a strong possibility of cross-contamination. Those people who are in the vicinity of a discharged firearm are liable to get the GSR from the air even if they have not touched the firearm.

Most importantly, the chemical tests for GSR are worthless because they give both false positives and negatives. For this reason, the FBI had rejected the so-called Paraffin or Dermal Nitrate test in 1935 itself. Many pieces of research, including those by H. W. Turkel et al and M. E. Cowan et al, confirmed that the test was useless. Charles O’Hara et al showed that the test is not even nitrated specific, but establishes merely that an oxidizing substance is present. FBI finally issued a formal order abandoning the test.

FBI expert Cortlandt Cunningham had testified before the Warren Commission that the unreliability of the paraffin test had been demonstrated by experiments run by the FBI even before the Kennedy assassination. Subjects were made to fire revolvers, automatics and rifles. The test yielded both false positives and negatives aplenty. The Warren Commission concluded, “The test is completely unreliable in determining either whether a person has recently fired a weapon or whether he has not.”

A. Maehly et al inform in their book that at the Interpol Conference in Paris in 1968, it was officially decided that the paraffin test should no longer be used. In their celebrated work ‘Current Methods in Forensic Gunshot Residue Analysis’, noted scientists A. J. Schwoeble et al conclude that all other chemical tests used for gunshot residue detection are also inherently unreliable.

How ignorance results in miscarriage of justice?

The fact that the Indian police and forensic labs are still using a test that was discarded by the world decades ago, and the defence lawyers are not challenging them, shows how utterly ignorant the system is. One example would suffice.

Without commenting on the judgments in the Batla House Encounter case of 2008, I must inform the readers that this rejected test was used in this case also. According to a report of Prasanna D. Zore in Rediff.com, police officers had proudly proclaimed that the dermal nitrate test on the hands of the two persons who were killed on the spot in the operation was positive. This means that as far as the police and its ignorance were concerned, a mere chemical test of dubious merit was adequate to establish that the deceased had indeed fired at the police!

At least in future, if we have to prevent miscarriages of justice, the legal fraternity must point it out to the courts that, a positive GSR result can, at best, only show that GSR is present, not how it came to be there!

(To be continued…)

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Dr N C Asthana IPS (Retd)
Dr N C Asthana IPS (Retd)
Dr. N. C. Asthana, IPS (Retd) is a former DGP of Kerala and ADG BSF/CRPF. Of the 51 books that he has authored, 20 are on terrorism, counter-terrorism, defense, strategic studies, military science, and internal security, etc. They have been reviewed at very high levels in the world and are regularly cited for authority in the research works at some of the most prestigious professional institutions of the world such as the US Army Command & General Staff College and Frunze Military Academy, Russia. The views expressed are his own.


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