Forensic Ballistics: Who Did The Shooting?
A real treat for fans of early forensics. An actual piece written by one of the early giants in the field of Forensic Ballistics.
By Calvin H. Goddard (1927)
In a county in Western New York a man was found guilty of a double murder on the opinion of a firearms "expert" that the bullets remove from the bodies had issued from the defendant's revolver. The case aroused the interest of Charles E. Waite, a lifelong criminal investigator, then attached to the office of the State Attorney General. He proved the bullets could not possibly have come from the weapon in question, established the innocence of the convicted man and secured his pardon, and brought about the arrest of the actual murderers.
From that time, twelve years ago, Waite devoted his life to establishing a system of bullet and firearm identification which would require no "opinion' of experts to substantiate it. It was to deal with facts, and facts alone. In ten years he visited every pistol and revolver factory in America, and many in Europe, gathering a mass of data about weapons and their manufacture. Later he and I joined forces, adding as associates Philip O. Gravelle, a master of photography and John H. Fisher, an expert in micrometrics. Since the death of Mr. Waite last year, I have continued the work.
Today the result of our efforts is a new science of identifying weapons - a science as exact and conclusive as that of tracing criminals by their fingerprints founded on the revelations of the microscope and precision measurements within the ten thousandth of an inch.
This science bears the rather high sounding name of "forensic ballistics. Actually, though, it is simplicity itself. Like the fingerprint system, it is based on the fact that no two things ever are exactly alike. A bullet fired through a pistol, revolver or rifle invariably bears certain distinctive marks or scratches - the "fingerprint" of that particular weapon's barrel. Even bullets fired from two weapons of exactly the same make and type and made by the same machine and tools, bear characteristic imprints which even untrained eyes can distinguish under the microscope.
Moreover, the shell from which a bullet is fired also bears individual marks made by the firing pin and breech block of the weapon. We have developed scientific methods of employing these marks to trace a bullet or shell to the weapon from which it came; and of proving whether a certain bullet could possibly have been fired from a given weapon.
Perhaps I can best give an idea of the methods by describing briefly my recent tests of the bullets, shells and pistol in evidence in the famous Sacco-Vanzetti murder case, in which Nicola Sacco and Bartolomeo Vanzetti were put to deal for the murder of a factory paymaster and his guard at South Braintree, Mass., in 1920.
While the appeal from the sentence was under consideration by Governor Fuller last summer, I offered to make the tests. The pistol in question was a .32 caliber Colt automatic; Sacco had admitted its possession. While the prosecution and its experts had contended that at least one of six bullets from the bodies of the murdered men had issued from that weapon, the defense with equal vigor had denied this contention.
My sole purpose, in the interest of justice, was to establish the truth of the matter by the unbiased evidence of science. The offer was made first to the defense, which declined it; then to the prosecution, which accepted. Entirely irrespective of the guilt or innocence of the defendants, or whether they received fair trial, the test established beyond contradiction these two long-disputed points:
First, that the so-called fatal bullet, No. 3, one of four from the body of Berardelli, the paymaster's guard, was fired through the Colt automatic subsequently found in the possession of Sacco and could have been fired through none other.
Second, one of the six shells picked up at the scene of the murder and known as "Fraher shell No. 3." was fired in Sacco's pistol, and could have been fired in none other.
Those facts were revealed by the microscope so clearly that any layman might see them for himself, and so convincingly that an expert for the defense, in my presence, agreed in astonishment that they were beyond dispute.
In the Court House at Dedham Mass., I conducted the tests in the presence of a professor in the Massachusetts Institute of Technology, who was an expert representing the defense; the Assistant District Attorney in charge of the case, a member of defense counsel, the Clerk of the Court, a stenographer and four newspaper men.
First I explained why every weapon leaves its own distinctive imprint on the projectiles it fires. In making a pistol or rifle barrel, the first step is to bore a hole through a cylindrical steel bar. Then a reamer smooths the rough inner surface. Next comes "rifling" - cutting a series of extremely shallow grooves, running spirally through the length of the barrel, to impart a spin to the bullet as it passes through. The surfaces between the grooves are known as the "lands." The grooves vary in different makes of weapons. In some there are five, for example; in others, six. In some they are arranged to give a right-hand twist; in others, left-hand.
In The barrel of the Sacco pistol, there are six grooves, with left-hand twist. Each spiral makes one turn in sixteen inches. The depth of the grooves is .0035 of an inch; their width, .108 of an inch; the width of each land is .051 of an inch.
Now, the marks by which any bullet may be identified are due largely to the tool called the rifling cutter, which cuts the grooves. To the unaided eye the sharp edge of this tool appears perfectly even; but actually, as in the case of a razor, the edge consists of a row of minute saw teeth, visible only under the microscope. These teeth leave microscopic scratches and ridges on the inner surface of the barrel. And when a bullet is fired through, these irregularities are impressed upon it in the form of very fine lines running parallel to the deeper lines cut by the groove edges.
Since no two rifling cutters can have little saw teeth exactly alike, no two pistol barrels can have exactly the same markings. Moreover, the edge of a cutter changes with every cut; hence, even if two barrels are rifled on the same machine and with the same tool, the markings they leave on bullets will differ.
A similar thing happens in the case of the breechblock and firing pin of a pistol. In filing down the breechblock the file invariably leaves distinction scratches, which are never the same on any two arms. Later, when a bullet fired, and the shell is hurled back against the breech with a force of some 10,000 pounds pressure to the square inch, the breech acts as a steel die, impressing its file pattern indelibly on the copper primer or cap of the shell. Thus the breech of every gun leaves its own distinct pattern.
Moreover, no two firing pins are ever the same in contour, even if made on the same machine. Consequently the dent made by the firing pin of a certain gun on the primer of a shell is an identity mark for that gun and no other. In short, every weapon in the world leaves its individual telltale fingerprints on every bullet and shell it fires.
In the Sacco-Vanzetti case there were four bullets from the body of Berardelli, the guard, and two from that of Parmenter, the paymaster. In the tests at Dedham the Berardelli bullets were the only ones in question. In addition there were six shells picked up at the scene of the murders. And, for comparison, a number of test bullets and shells subsequently fired from the Sacco pistol by representatives of both prosecution and defense. By comparing the murder bullets, one by one, with the test bullets, my object was to establish whether any of the former came from Sacco's weapon, and if so, which one or ones.
For this I used an instrument called a comparison microscope, invented by Philip O. Gravelle. This is really two microscopes in one, fitted with prisms so arranged that when two objects are placed beneath, the left half of one and the right half of the other are center in the single eyepiece. This has the effect of fusing the opposite sides of the two objects into a single image. The extent to which the two halves match is a measure of the similarity of the objects.
First I examined the shells. Under the microscope I placed one of the murder shells and one of the test shells, with the caps facing upward. Examination quickly showed that they could not have come from the same weapon, for the imprint of the firing pin was entirely different in the two halves. The substitution of a different test shell brought the same result.
Next I tried a second murder shell. This likewise was decidedly different from the test shell, both in the imprint of the firing pin and in the absence of certain ridges which appeared across the cap of the test shell. It was impossible to match the two halves.
But the third murder shell matched perfectly with the one known to have been fired from Sacco's automatic. There was no question that the two came out of the same gun. The firing pin imprints were of exactly the same diameter, and the markings imprinted by the breechblock were identical. Holding one of the shells stationary, I carefully turned the other until both were in the same phase, - that is, until the features of the opposite halves matched at the center line. The imprints - scratches and ridges - matched all the way across the face of the shell.
The identity of these "fingerprints" is revealed in the microscopic photographs of the two shells. At the right is the murder shell in evidence; at the left is the test shell fired in the Sacco pistol. If you look closely you will see the similarity of little V-shaped scratches on both primers. Then if you compare the other scratches and ridges you will see that in every case they are of the same dimensions and in the same relative positions.
The identity is equally clear in the imprints of the firing pin at the center, even though the test shell at the right bears the additional imprint of the trade mark "W'.' Observe especially the deep setback or indentation at the left of the firing pin imprint in each case. You will see, of course, that neither the firing pin marks nor the imprints of the breechblock as a Whole are in exactly the same relative position on the two shell caps. In any firearm there is a certain amount of play, and the shells do not always come back against the breech in exactly the same position; nor does the firing pin always strike the exact center of the primer. The positions of the individual markings in relation to the imprint as a whole are, however, identical.
Under the microscope I compared this murder shell with other test shells fired from the Sacco pistol. Although the latter were somewhat fouled and dirty, the identity was again evident; so evident in fact, that the defense expert, looking through the microscope exclaimed: "Well, what do you know about that!"
Finally I tested a fourth murder shell in the same manner. There was no similarity. Then I applied the tests to the four bullets from the body of Berardelli, comparing each with test bullets fired from the Sacco pistol into a box of sawdust. In each case the bullets were placed horizontally under the comparison microscope in little holders which enable them to be rotated.
The first one I examined, known in the evidence as fatal bullet No.3, was considerably fouled and corroded, but the microscope revealed beyond question that it had come from Sacco's weapon. First, the marks of the rifling grooves were of the same width and the same angle as those of the test bullets. In addition there appeared tiny scratches which were identical. In particular, the microscope revealed one very prominent gouge which matched perfectly. Rotating the bullets, I compared them groove by groove. I invited the defend expert to look into the microscope.
"That," he said, referring to fatal bullet No.3, "could not have come from any other gun."
None of the other body bullets matched. For example, one of them, bullet No.2, obviously, came through a right-hand twist pistol, where as Sacco's was left-band twist.
Returning again to fatal bullet No.3, at the defense expert's request I compared it with other test bullets, one by one. The marks of identity - tiny scratches and grooves - matched in every case.
Further evidence in corroboration was the fact that fatal bullet No.3 was of an obsolete type, manufactured with grooving near the bas known as the "cannelure" - a remnant of the old days of lead bullets. Three bullets of this type were found on Sacco's person.
No doubt many persons, including some officials, are skeptical of this sort of comparison evidence. "Guns leave their fingerprints Nonsense!" you may hear them say. Yet only twenty-five years ago everybody ridiculed Joseph A. Faurot, former deputy police commissioner of New York, for trying to secure recognition of human fingerprinting as a mean of identification. Faurot lived to see the fingerprint system adopted throughout the world, and also to say of the new method of identifying bullets and firearms:
"It is a science, in my opinion, as infallible, as practicable, as revolutionary, and as valuable in criminology as fingerprinting itself."
Today in our laboratories in New York City we have records of the shop standards entering into the manufacture of virtually every modern revolver and automatic pistol of both American and foreign makes, a collection of many hundreds of bullets of all calibers and types, fired through arms of nearly every make; and about five hundred revolvers and pistols from all parts of the globe. Given any bullet, we are ordinarily able to determine within a short time exactly what kind of weapon fired it; and if that weapon is eventually traced and found, we can identify it with scientific exactness.
With a remarkable instrument called a helixometer, designed by Mr. Fisher, we can examine the entire interior of the barrel of a weapon. It reveals every flaw, fouling deposit or rust spot that might be reproduced on a bullet fired through it. Moreover, by studying the deposits within the barrel we can determine the approximate time when the weapon was last fired, the kind of powder in the cartridge (black or smokeless), and sometimes the type of bullet.
Still another valuable instrument is a micrometer microscope with which we can measure the width of a riding groove to the ten thousandth of an inch. With the same accuracy we can measure the depth of the groove, its angle, and the pitch of the spiral.
We have collected specimens of the different kinds of powder grains used by virtually every manufacturer of projectiles. When a pistol is fired, usually some powder grains are discharged unburned. At close range some of these grains may lodge in the flesh of a victim. By examination and comparison with the specimen grains, we can determine the manufactures of the powder charge in the fatal cartridge.
By such methods we are supplanting "expert opinion" with facts. Our goal is that innocent men shall not be sent to their deaths, not guilty men acquitted, by testimony unsubstantiated by the facts of exact science.
Who is Calvin Goddard?
Calvin Goddard examining a revolver barrel with the crime laboratory's helixometer. Al Capone Museum
Colonel Calvin Hooker Goddard (1891 – 1955) was a forensic scientist, army officer,academic, researcher and a pioneer in forensic ballistics. He was born in Baltimore, Maryland. After graduating from the Boys' Latin School of Maryland in 1907, Goddard graduated with a Bachelor of Arts degree in 1911 from the Johns Hopkins University and then earned a medical degree and graduated in 1915.]Career
He joined the United States Army and became a Colonel. He was also a professor of police science at Northwestern University and the Military Editor of the Encyclopedia Britannica. He was also the editor of the American Journal of Police Science, America’s first scientific police journal. Colonel Goddard commanded the US Army Crime Laboratory in Japan for a number of years after World War II. Calvin Goddard brought professionalism, the use of the scientific method, and reliability to Forensic Firearm Identification, at a time when charlatanism was rampant in this field. His testimony in 1923 in the Frye case and others, paved the way for judicial acceptance of Firearms Identification. According to Goddard's grandson, he may have been the only army officer who served in four branches: Ordnance Corps, Military Police Corps,Medical Corps and became a Military Historian.
In 1925 Goddard wrote an article for the Army Ordnance titled "Forensic Ballistics" in which he described the use of the comparison microscope regarding firearms investigations. He is generally credited with the conception of the term "forensic ballistics", though he later admitted it to be an inadequate name for the science. In April 1925, Major  Goddard established the Bureau of Forensic Ballistics in New York City with C. E. Waite, Philip O. Gravelle and John H. Fisher. The Bureau was formed to provide firearms identification services throughout America. Goddard researched, authored and spoke extensively on the subject of forensic ballistics and firearms identification, becoming the internationally renowned pioneer in forensic ballistics. The Bureau of Forensic Ballistics, United States’ first independent criminological laboratory, which Goddard headed, and where ballistics, fingerprinting, blood analysis and trace evidence were brought under one roof. When the Lab began publishing the American Journal of Police Science, which was edited by Colonel Goddard, Hoover strongly encouraged his Special Agents in Charge to subscribe to it and he supplied articles on fingerprint issues and Bureau responsibilities to the journal. The following year the Bureau contributed three articles for the journal’s series entitled “Organized Protection Against Organized Crime.” Hoover also sent a number of representatives to a symposium that Goddard sponsored on scientific crime detection. He was also an advisor to FBI when they set up a similar Forensic Laboratory.
Goddard with Comparison Microscope
Philip O. Gravelle, developed comparison microscope for the identification of fired bullets and cartridge cases with the support and guidance of Calvin Goddard. It was a giant leap in the science of firearms identification in forensic science. The firearm from which a bullet or cartridge case has been fired is identified by the comparison of the unique striae left on the bullet or cartridge case from the worn, machined metal of the barrel, breach block, extractor, or firing pin in thegun. It was Gravelle who mistrusted his memory. "As long as he could inspect only one bullet at a time with his microscope, and had to keep the picture of it in his memory until he placed the comparison bullet under the microscope, scientific precision could not be attained. He invented the comparison microscope and Goddard made it work." Sir Sydney Smith also appreciated the idea, emphasizing the importance of stereo-microscope in forensic science and firearms identification. He took the comparison microscope to Scotland and introduced it to the European scientists for firearms identification and other forensic uses.
Sacco and Vanzetti Case
Sacco and Vanzetti
Nicola Sacco and Bartolommeo Vanzetti were two Italian-born American anarchists, who were arrested for the murder of security guard Alessandro Berardelli and the robbery of US$15,766.51 from the factory's payroll in South Braintree, Massachusetts during the afternoon of April 15, 1920. During the trial a worldwide outcry arose, with the firm belief based on railroaded justice and racial prejudice. On April 8, 1927, their appeals exhausted, Sacco and Vanzetti were finally sentenced to death in the electric chair. A worldwide outcry arose and Governor Alvin T. Fuller finally agreed to postpone the executions and set up a committee to reconsider the case. By this time, firearms examination had improved considerably, and it was now known that an automatic pistol could be traced by several different methods if both bullet and casing were recovered from the scene.
Automatic pistols could now be traced by unique markings of the rifling on the bullet, by firing pin indentations on the fired primer, or by unique ejector and extractor marks on the casing. The committee appointed to review the case used the services of Calvin Goddard in 1927. Goddard used Philip Gravelle's newly-invented comparison microscope and helixometer, a hollow, lighted magnifier probe used to inspect gun barrels, to make an examination of Sacco’s .32 Colt, the bullet that killed Berardelli, and the spent casings recovered from the scene of the crime. In the presence of one of the defense experts, he fired a bullet from Sacco's gun into a wad of cotton and then put the ejected casing on the comparison microscope next to casings found at the scene. Then he analyzed them carefully. The first two casings from the robbery did not match Sacco’s gun, but the third one did. Even the defense expert agreed that the two cartridges had been fired from the same gun. The second original defense expert also concurred. The committee upheld the convictions. Nicola Sacco and Bartolomeo Vanzetti were found guilty and executed via electrocution in Massachusetts on August 23, 1927.
What is a Comparison Microscope?
A comparison microscope is a device used to observe side-by-side specimens. It consists of two microscopes connected to an optical bridge, which results in a split view window. The comparison microscope is used in forensic sciences to compare microscopic patterns and identify or deny their common origin. Without this device, the identification of tool marks and firearms would be such a cumbersome process that it would be carried out on a very limited basis.
The idea behind the comparison microscope is simple. Two microscopes are placed next to each other and the optical paths of each microscope are connected together by the optical bridge. The optical bridge consists of a series of lenses and a mirror that brings the two images back together at the single eyepiece. The user looks through the eyepiece as with a regular microscope, except that a line in the middle separates the circular view field into two parts. The left side of the view field is the image produced by the left microscope, and the right side of the view field is the image produced by the right microscope. In some more modern or sophisticated comparison microscopes, it is also possible to super-impose the view fields generated by the two microscopes. This is particularly convenient when the forensic scientist compares impressed patterns rather than striated patterns. It is important that the two microscopes are identical. In order for a comparison to be valid, the two images produced in the circular view field needs to be at the same magnification and present the same lens distortion (if any). Comparison microscopes are mostly used in a reflected light setting, but a transmitted light setting is also available in some instances, and fluorescent light settings are found on higher-end models. This allows for comparison of more than just bullets and toolmarks.
Use of a comparison microscope is straightforward. The incriminated impression, typically a bullet or casing found at a crime scene or a toolmark's cast from a crime scene, is placed under the left microscope and thus, appears in the left part of the circular view field. A comparison impression, such as a bullet fired from a revolver found on a suspect, is placed under the right microscope and thus, appears in the right part of the view field. When comparing striations, the forensic scientist moves the comparison object until the striations match the ones present on the incriminated object. If the striations do not present similarities, then the two objects cannot be associated with a common origin. If the striations match, then a common source between the two objects is established. When comparing impression marks, the forensic scientist can use the superimposition option and, again, by moving the comparison object on the right, try to find common characteristics between the two objects.
The comparison microscope is used to compare impression evidence that requires a magnification ranging from 5× to approximately 100×. Items that are commonly observed under the comparison microscope are fired bullets, fired casings, and toolmarks. These items are observed under a reflected light setting. Other evidence, including impressions of serial numbers or characters from a typewriter, can also be compared using the comparison microscope. These are compared using a reflected light setting. This comparison might allow for the link between a stamped serial number and a die or between a sheet of paper bearing characters and the typewriter that was used to write it. The comparison microscope is also used to compare layers of a paint chip. This might allow for the identification of the vehicle from which the paint originated. Finally, when used in a transmitted light setting, hair, fibers, or the extruding striations of plastic bags can be compared. This allows the comparison of fibers found on a seat with the clothing of a suspect, for example. Plastic bag striations might establish links between different plastic bags and to demonstrate that they originate from the same batch. This is particularly useful with the small bags used to sell drugs. When dealing with fibers and plastic bags, the comparison microscope can also be used in an ultraviolet light setting or a polarized light setting.
A modern comparison microscope
The comparison microscope was invented in the 1920s by American Army Colonel Calvin Goddard (1891–1955) who was working for the Bureau of Forensic Ballistics of the City of New York. Goddard also benefited from the help of Colonel Charles Waite, Philip Gravelle, and John Fisher. At that time, the comparison microscope was used to compare fired bullets and casings. In the late 1920s, Swedish criminalist Harry Söderman (1902–1956) drastically improved the comparison microscope by inventing a system for rotating the bullets under the objectives. This allowed for a much faster comparison of lands of grooves of bullets by simultaneous rotation of both the suspect and comparison bullets. Söderman gave the name Hastoscope to his invention.