The bullets lay in yellow evidence envelopes and the gun in a white cardboard box on a grey government table. The red-faced evidence sergeant with a detached attitude sat on one side of the table. Two prosecutors glowered blackly from the head of the table. A defense attorney reached for an envelope provoking a prosecutor to scream "You can't open that!" There was no way to examine the evidence without opening the envelopes and boxes. The defense lawyers looked at the evidence sergeant who looked indifferently at the table. A motion and hearing produced an order allowing the defense to examine the evidence. At the hearing the judge pointedly asked the defense what they thought they would learn from examining the evidence. The defense had no idea until it could examine the evidence. However, "we don't know" are not a great argument. The defense cited their ethical obligation to examine the evidence. Ethics always provides a great argument. The judge lectured that it was not possible to match a bullet to a box of ammunition, something the FBI had just admitted after sending people to prison on such pseudo-science. The defense had not said they would try such a thing and linking a bullet to a box was not an issue in the case. But the defense endured the rant in order to get access. Access was granted, but the prosecution insisted on being present when the evidence was examined. The defense was not granted a similar limitation.
Everything that touches a cartridge leaves evidence behind. The magazine lips scrape the sides of the cartridge case; the chamber leaves marks as the case swells on the force of the explosion. The face of the bolt marks the base of the cartridge. The firing pin marks the primer, the extractor marks the rim and the ejector leave a mark as it kicks the case out of the gun. Rifling leaves its unique mark on the projectile. Broken or mutilated bullets may be difficult to match but ballistic technology marches on. In 1920, the .32 bullet recovered in the Sacco and Vanzetti case could not be matched to Mr. Sacco's 1903 Colt .32ACP. In 1961 it was positively matched. 1 Shotgun barrels may leave marks on the plastic cup if the barrel has been crudely sawn off. Imperfections in the barrel may do the same. Objects the bullet hits before striking the target may be reflected on the bullet, especially hollowpoint bullets. This may show where the gun was aimed or the positions of the parties at the time of the shooting.
A German company believes that it can pinpoint the organ a bullet passed through. It used mass spectrometry to identify proteins on the bullets. 2
In one case a bullet could not be matched to any firearm possessed by the suspect, but the cartridge case showed that it had been previously ejected from a second gun in the suspect's possession. This did not prove that the suspect ejected the cartridge from the second gun much less fired the murder weapon, but it was one of many little things adding up to a life sentence.
Television programs have portrayed bullets being fed into the IBIS program and promptly matched to a specific gun. It cannot be too strongly stated that these programs are fiction. There have been successful matches of bullets fired within days of each other at different crime scenes. This has sparked demands for a database of bullets from every gun produced or imported into the United States. The California Department of Justice tested this demand by firing bullets from a number of new pistols and attempting to match the first with the last round fired. It failed. The test came back with a great number of false positives, which in the real world would link an innocent person to a shooting. Repeated firing wears the barrel and changes the markers identified by computers. Human examiners may be able to link two such bullets where computers cannot. New York State has insisted on a computer database but cannot show a case it has solved. In 2015 Maryland ended its ballistic collection due to a similar failure.
Not all of these marking are conclusive. Steel casings absorb fewer and less distinct markings than do brass cases. Steel cases are found in Russian manufactured ammunition. 3
Powder impressions on the lead base of bullets may show the type of gunpowder used in the cartridge, and thus the brand of ammunition. Ammunition companies vary their gunpowder formulas from time to time for reasons known to themselves and ballistics experts. This can change the size of the gunpowder residue around a wound and the impressions on the base of a bullet. This can change what the evidence says.
Gunpowder impressions on the base of a bullet will not identify the shooter, but may show a sequence of shooting. A man claimed his shooting was in self-defense, pointing out the warning shot in the ceiling. He had a mix of cartridges in his revolver and the bullet in the ceiling was linked to the second shot fired. The fake warning shot may have been an effort to "improve" the evidence but the lie served to have him charged with murder.
Gunshot residue will often mark a shooter's hand, possibly both hands possibly clothing and face. It may also mark structures and people adjacent to where the gun was fired which can demonstrate where the shooter was standing. Back blast from the target, mostly blood, may also mark the shooter at a range of about three feet.
The following page contains a table showing common sources of false positives for gunshot residue (GSR) from Hueske, Edward E. Practical Analysis and Reconstruction of Shooting Incidents CRC Press Boca Raton Fl 2006 at 140. It is also possible that if a police officer draws his gun on a subject, then holsters his gun and handcuffs the subject he may transfer GSR to the subject.
Swabs are used to collect gunshot residue from persons, clothing and objects. These are analyzed by a scanning electron microscope/energy-dispersive x-ray spectrometry. The swabs may destroy fingerprints and DNA. The analysis detects substances from the primers of cartridges. Different companies use different materials in their primers which may narrow down what ammunition was fired.
The machine must be calibrated before use. Tests must be done in a room free of possible contaminates. Experts advise that guns should not be taken into the room and it should not employ persons who fire guns.
Lack of GSR does not mean that the subject did not fire a gun. It only means that GSR was not detected. If GSR is detected, and environmental contamination is excluded it can only be said that the subject fired a gun, was in the vicinity of a gun when it fired or was handled by someone who fired a gun.
A gun will seldom show fingerprints. The surface of a gun is treated to prevent rust. This also serves to resist fingerprints. Fingerprints carry moisture and salt which serve to corrode metal. Twenty years ago, a firearms company's advertising stressed that its products were proof against fingerprints and this was taken as directed to criminal use. Fingerprints have been taken from guns, sometimes from the internal surfaces of gun and sometimes from cartridges. In one case a cartridge case did not show fingerprints, but after being heated the salts left by the shooter's finger created a print that was sufficient for a conviction.
DNA (of course)
DNA comes into play; of course. It is caught in the grips of guns and the sharp edges of internal parts and magazines take their own samples. The Colt 1911A1 is infamous for "hammer bite." On recoil the hammer takes a bite out of the web between the thumb and forefinger. This can identify a person who has fired a gun and link him to the gun used. It does not always happen. Backblast from the shot leaves DNA on the shooter at close range.
When police have a shooter and a gun in hand the forensic examination will be limited. In one case a citizen fired nine rounds from his SKS rifle at an intruder. Six rounds struck the intruder. Confronted with an empty 10-round SKS rifle the investigators did not look for the remaining bullets and did not even find three cartridge cases a few feet from the other six cases in the defendant's living room. 4 The CSI team will not be called to collect every hair and fiber. If they did in reality what they do on that show, their budget would last about a week.
It is often necessary to bring in experts or investigators. In a couple of cases there was a dispute over where bullets landed. The defendant claimed they were warning shots, and the complaining thugs spun imaginative stories about hearing the whistle of bullets or having dirt kicked on them by the impact of bullets. Private investigators with metal detectors found the bullets exactly where the defendant said they would be. They were specifically instructed to cover the entire area and all uncovered bits of metal were displayed for the jury in clear evidence bags to prevent claims of planted evidence. 5
Cartridge cases are thought to land to the right of where the gun if fired, but this is not true. 6 A study by the Force Science Institute demonstrated that the way the gun is held determines the ejection pattern. The load of gunpowder in the cartridge case, type of gun, condition and lubrication of the gun also have some effect. Cases are light, they roll, they are blown by wind and traffic, they are caught in shoe treads and carried away, but prosecutors file based on where they are found.
In another case the trajectory of the bullet was fixed by sheriff's deputies by tacking a string to the bullet hole left in a wall and stretching a string; a useless exercise. 7 High school geometry teaches that two points make a line. A proper trajectory was determined by John Cayton of Access Forensic Laboratory. 8 A wooden dowel rod was inserted into the hole and a string run from an eyelet screwed into one end. This allowed a more accurate trajectory later confirmed with lasers. 9 An accurate trajectory showed where the dead man and the shooter stood. This confirmed the defendant's statement and he was acquitted. Straws, tubes and brake lines come in appropriate sizes.
Trajectory will be more precise if the precise caliber is known. Centerfire rifles cartridges exist in .22, .221, .222, .223, .224 and at one time there was a .225 cartridge. The human eye is not calibrated to determine the difference between a .44 and .45 hole. A manual the size of Black's Law Dictionary lists the cartridges manufactured since 1850; most of these can still be encountered. A common projectile is about 3/8 th of an inch in diameter (give or take a few hundredths of an inch). These are found in .38/.357 and 9mm cartridges. There are approximately 20 different cartridges which fire a projectile that is 3/8's inch in diameter. Some of these are rare but no one can look at a bullet hole and testify to a reasonable scientific certainty that it is a 9mm parabellum or .38 special. 10 A .38 bullet is actually .36, it is the cartridge case that is .38 inch.
A load of buckshot expands at an approximate rate of one inch per yard between the muzzle and target. Other types of shot expand at different rates. This will determine the approximate location of the shooter. When a load of shot strikes the target at an angle it leaves an oblong pattern. A mathematical formula can convert this to a circular pattern. However, we do not enter into mathematics without a native guide.
Trajectory would be more precise if bullets made precise holes. A bullet may tumble in flight because of being fired in an oversized barrel or striking something in flight. A bullet may strike sideways or backwards. A formula exists for determining caliber from irregular holes however this is a matter for experts.
ENTRY AND EXIT
An entry hole in a rigid material may be larger than the projectile. An entry hole in an elastic material, like human flesh, may be smaller than the projectile. The elastic material will stretch before penetration and then snap back. This may cause a bruise around an entry wound in skin which can be mistaken for powder burns.
The entrance and exit wounds must be clearly identified. Powder burns around the wound and bruising indicate entrance wounds. Exit wounds are typically, but not always, larger than entrance wounds. Bullet "whipe" will show fibers and sometimes skin pointing in the direction of travel; at the exit wound. This is a matter for expert testimony after considering all factors.
One must get a real expert. A mid-Missouri man killed a burglar, the round entering the chest and exiting the back. The burglar's family sued claiming that the back wound was the entry on the testimony of a paramedic, who had seen a bullet wound before, over that of a forensic examiner who had done over 2,000 gunshot autopsies. A fragment of the burglar's T-shirt was found lodged in the back of the burglar's jacket where it had been carried by the bullet. The family continued to insist their burglar had been shot in the back. In another case a north Missouri assailant (whom the prosecution insisted on calling a "victim") claimed that he was walking away from the defendant when shot. Locked into this testimony by multiple statements it was demonstrated through medical records that the bullet would have had to turn corners to have entered his leg as he claimed. The prosecutor did not change his position.
Powder burns around a wound indicate an entry wound. The size of the powder burn around the wound can prove how far away the criminal was when shot. However, this varies with the brand of ammunition, as the various companies use different formulas for their gunpowder. It may vary with lot number as companies change their formula.
Outside objects may affect the size of the powder burn, absorbing or dissipating the powder before the bullet strikes. Sometimes there is just a mystery. The autopsy on Senator Robert F. Kennedy found gunpowder residue which was not consistent with the reported distance the assassin was from the Senator. Either tests were done with the wrong type of ammunition, the assassin tampered with his rounds, there was a second assassin or some still-unknown factor. 11
SEE THE GUN
In a Felon in Possession case we asked to see the gun. The ATF agent on the case told us that we were the first lawyer who had asked to see the gun before trial. We find this difficult to believe. In any gun case it is important to determine if the gun is a gun. If it does not function, or if it misfunctions that could be the start of a defense. Some guns are etched with skulls, confederate symbols or macho sayings. These may not be obvious in discovery photocopies of pictures. The client may very well have a reason for these embellishments. It would help to have such an explanation organized before the jury sees the weapon.
It may be important to have a gunsmith examine the firearm. If a gun will not fire, it is not a gun and not a crime.
Know how to hold and operate the gun. Do not point it at anyone. When the officer is asked to identify the gun, make a pointed motion that it be checked for ammunition. Juries react favorably to safety.
In a homicide case, file a motion in limine to keep out the death certificate. Under cause it death this document will read "homicide." Technically this is correct. It means death by human hands. To a jury it is synonymous with murder. Ask that all witnesses be ordered not to refer to the death as a homicide.
It is often desirable to have the jury view a shooting scene. Shootings are often at very close quarters in very cramped spaces. The prosecution will demand to know why the defendant did not retreat. We do not have a "stand your ground" law in Missouri. Showing the scene demonstrates the impossibility of retreat. In one case a man killed an MS 13 member in a vast parking lot at 3 AM. At trial the investigating defective insisted that the defendant could have retreated. There was no open business within a mile of the location. On cross examination the detective was asked to where the man could have retreated. The detective insisted that he could not understand the question. He continued to claim he did not understand these basic English words. A view of the scene would have made his obstinacy an obvious subterfuge.
Sometimes it is not possible to view the scene. A view of the scene cannot be introduced into evidence and taken back to the jury room. Photographs are basic; blown up to poster size is better. In one case an architect made a scale drawing of the scene and an acetate covering could be dropped over it to show the trajectory of the bullet and positions of the parties. A scale model of the scene is often better. A mannequin can be used to show entry and exit wounds.
Recently lasers have been used to map crime scenes and traffic accidents. The FARO company makes a handheld laser which can make 3-dimensional models indoors and outdoors. See www.faro.com/focus.
Blood spatter will be of "high velocity" which shows up as small droplets. It will require an expert to determine the meaning of blood spatter and the experts credentials should be examined. Blood will spatter from entry wounds as well as exit wounds. At very close range, about three feet, the shooter may get some of this spatter on him. It may be a fine mist and may not show up without testing.
People move after being shot. In one instance a man's heart was shredded by a shotgun blast and he still ran 68 feet. Deer hunters have seen deer run for considerable distances with fatal wounds. If this is an issue in a case it may be wise to get hunters on the jury.
After a shooting blood with be sprayed, smeared, wiped, dripped and tracked. Animals have gotten into shooting scenes and spattered blood around. Insects have gotten into the blood and flying away left a fine mist of droplets which could confuse the scene.
It is necessary to take a holistic view of all of the evidence in recreating the scene. The Innocence Project has no end of cases in which one piece of evidence, often misinterpreted, was used to define the case. Tunnel vision precluded investigators from noticing other evidence that conflicted with their initial interpretation. Very often conflicting evidence was re-interpreted to support the initial theory.
Under stress individuals may not perceive reality correctly. In one case a traffic stop went bad and the driver tried to turn the wheels and drive away. The officer believed that he was going to be run over and killed the driver. Investigation showed that the vehicle could not turn tight enough to endanger the officer. However, there is no way for the officer to know that at the time.
In gunfights many things happen, all at the same time and very quickly. In the "Gunfight at the OK Corral" the gunfight was in an area the size of a living room. Thirty shots were fired in thirty seconds, three men were killed and two wounded. Despite the transcript from the inquest, historians still dispute who fired first. Participants had different stories, even participants on the same side.
A motion in limine should be filed to exclude the death certificate. For cause of death it will say "homicide." The jury will take this as a synonym for murder.
 www.accessforensiclab.com. His resume goes on for over 11 pages. He once identified a Civil War pistol ball found in the body of Jesse James. Jesse is dead, get used to it. Mr. Cayton has retired, and we cannot get used to it.